research questions about nuclear weapons

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What Questions Should Humans Be Asking about Nuclear Weapons?

In June 2023, we asked ChatGPT this question. Here is its exact response — unedited, uncorrected, uncanny

Question : What questions should humans be asking about nuclear weapons?

ChatGPT Answer:  Nuclear weapons are one of the most destructive and deadly weapons ever created, and their existence poses a significant threat to global security. Here are some questions that humans should be asking about nuclear weapons:

• How can we prevent the use of nuclear weapons? This includes preventing nuclear war, accidental detonations, and unauthorized access to nuclear weapons.
• What are the risks associated with nuclear weapons? This includes the potential for nuclear accidents, the environmental and health impacts of nuclear testing and use, and the geopolitical risks associated with nuclear proliferation.
• What role should nuclear weapons play in national security strategies? Is it ethical to possess and potentially use such destructive weapons, and what are the potential consequences of doing so?
• How can we reduce the global nuclear weapons stockpile? This includes arms control agreements, disarmament efforts, and the safe and secure storage and disposal of nuclear materials.
• How can we address the challenges posed by emerging technologies, such as hypersonic missiles, in the context of nuclear weapons?
• How can we improve international cooperation and dialogue on nuclear weapons? This includes diplomatic efforts to reduce tensions and increase transparency between nuclear-armed states.

These are just a few examples of the many questions that humans should be asking about nuclear weapons. It is important to have ongoing discussions and evaluations of nuclear weapons policies and strategies to ensure that we are reducing the risks associated with these weapons and moving towards a more peaceful and secure world.

ChatGPT is an artificial intelligence-powered language model developed by OpenAI.

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Thinking about the Unthinkable: Five Nuclear Weapons Issues to Address in 2024

Photo: Mikhail Svetlov/Getty Images

Commentary by Kelsey Hartigan

Published February 9, 2024

As the United States gears up for a presidential election and the administration juggles support to Ukraine, growing conflict in the Middle East, and a host of other challenges, Washington will need to address five key nuclear weapons challenges in 2024. Managing Russia’s nuclear threats, China’s opaque nuclear buildup, and North Korea’s increasing provocations—and the increasingly close relationships among them—will be no easy feat. At the same time, Washington will need to navigate its extended deterrence commitments and efforts to better integrate with U.S. allies and finally organize for a series of consequential, long-term decisions on the future of the U.S. nuclear arsenal. While a high-intensity war with China or Russia or a major conflict with North Korea is not inevitable, the pathways to potential conflicts are increasing, and so too are the risks of nuclear use—especially limited nuclear use. With an exceedingly complex international security environment, policymakers, planners, and legislatures need to think about the unthinkable this year and take action. Detering nuclear use requires a sober assessment of the new and changing ways adversaries are attempting to leverage nuclear weapons and clear-eyed plans for how to manage nuclear threats if deterrence fails.

Here are the top five nuclear issues to address in 2024:

• Russia’s Nuclear Threats and the War in Ukraine

As the war in Ukraine enters its third year and the administration and Congress debate future U.S. security assistance to Ukraine, a key question will be how Russia’s nuclear signaling and threats will evolve in 2024 and how the trajectory of the conflict will affect the potential for nuclear use. While the risk of use likely remains low amid the current stalemate, significant changes on the ground, such as a significant spike in attacks deep inside Russia, could affect that calculus. In addition, with increased cooperation between Russia and North Korea (and Iran) and confirmation that North Korea is providing Russia with ballistic missiles and ballistic missile launchers, another key question will be to what extent this kind of assistance affects the situation on the ground, whether this prolongs the conflict, and how this affects overall escalation dynamics. With the intelligence community assessing that “Moscow will become even more reliant on nuclear, cyber, and space capabilities as it deals with the extensive damage to Russia’s ground forces,” nuclear risks could actually grow in the coming months and years, making it essential that Washington, NATO, and Kyiv remain prepared and clear-eyed about how to handle a range of scenarios, especially those involving “ battlefield” nuclear weapons and limited nuclear use.

In addition, while U.S. officials have indicated that they have not yet seen changes to Russia’s strategic nuclear forces since it suspended New START, without onsite inspections or data exchanges, it may become more difficult over time to maintain confidence that there have been no militarily significant operational changes to Russia’s strategic forces using national technical means alone. This means there will be very few guardrails on the broader U.S.-Russia strategic relationship, making it—as well as Russia’s efforts to deliberately manipulate nuclear risks in Ukraine and beyond—one of the top nuclear issues to watch in 2024.

• China’s Nuclear Buildup

China’s rapid expansion and diversification of its nuclear forces also demands attention in 2024. While the administration has made clear that “the United States does not need to increase our nuclear forces to outnumber the combined total of our competitors in order to successfully deter them,” a number of recent high-profile commissions, reports , and studies argue for important changes to U.S. nuclear forces, setting up a renewed debate over what’s driving China’s nuclear buildup and whether and how the United States should respond . China’s nuclear buildup cannot be viewed in isolation, however. This is fundamentally a question of whether the United States has the necessary force structure to manage concurrent or sequential conflicts with two nuclear-armed adversaries—a force-sizing construct the Pentagon abandoned years ago (and never truly had to address in the same way).

At the same time, the debate over potential changes to the size and composition of U.S. nuclear forces cannot mask questions over how Washington and its allies would respond to Chinese nuclear coercion or even limited nuclear use in certain scenarios, particularly a Taiwan   crisis . Such a crisis could occur well before any changes to the current program of record materialize, and China is no doubt watching how Russia is deliberately manipulating nuclear risks in the war in Ukraine. With continued cross-Strait tensions and an uncertain future for the broader U.S.-China relationship, it is essential that officials understand the conditions under which China might use nuclear weapons and be prepared to manage the nuclear shadow that will loom over virtually any conventional conflict in the Indo-Pacific. Arms control talks with China may help improve this understanding over time, but recent efforts to engage on these issues are unlikely to translate into a reliable risk reduction mechanism any time soon or change the operational dilemmas U.S. forces might encounter. This means that Washington and its allies need to deepen planning and consultations in 2024 on managing the nuclear shadow with China for if and when a conflict occurs and ensure that these efforts are fully integrated into broader defense planning efforts.

• Tensions with North Korea and Opportunistic Aggression

In his New Year address, Kim Jong-unn warned that North Korea needs to prepare for war with the United States in 2024 and pointed to the U.S.-Republic of Korea (ROK) Washington Declaration, increased trilateral exercises, and the more visible presence of U.S. strategic assets as the reason behind the North’s aggressive posturing. While to some extent, this kind of rhetoric and blame game is more of the same— especially in an election year —North Korea’s continued quantitative and qualitative growth of its nuclear and ballistic missile programs, including both long-range systems capable of striking the United States and its increasing emphasis on tactical nuclear weapons, pose serious threats to the United States, ROK, and Japan that cannot be ignored or wished away. Washington and Seoul cannot deter missile tests or satellite launches, but they can take steps to ensure U.S. and ROK forces are prepared for both major conflicts as well as localized attacks , which can in turn help deter a war that no one wants. This requires consistently updating plans and assumptions, clarifying roles and responsibilities, and maintaining readiness for a wide range of North Korea contingencies. Maintaining this focus can be difficult given all of the demands on U.S. forces and the attention on great power competition, but it is essential.

At the same time, tensions on the Korean Peninsula don’t exist in a vacuum, and possible North Korean contingencies or conflicts cannot be planned against in isolation . As North Korea and Russia step up their cooperation, ties between Russia and China increase, and China and North Korea rekindle links, 2024 will unfortunately likely serve as a reminder that it is not enough to focus on managing individual flashpoints with Russia and China. If the United States finds itself in a conventional conflict with China or Russia, it could provide a dangerous opening for North Korea to exploit, just as a conflict with North Korea could leave the United States and its allies dangerously unprepared to manage a bubbling over of tensions with Russia or China (Russia and China could also of course take advantage of regional conflicts in separate theaters, which would pose even greater constraints).

Understanding and better preparing for the risks and tradeoffs associated with these types of opportunistic aggression scenarios, whether coordinated or not, should be a top priority in 2024. This will require, among many things, difficult and frank consultations on the limitations and possible roles and responsibilities across various alliance structures in the Indo-Pacific, as well as with NATO allies.

• U.S. Extended Deterrence Commitments and Integration with U.S. Allies

U.S. allies are understandably skeptical over whether the United States can and will maintain its alliance commitments. Managing these concerns—especially in an election year—will require continued time and attention, a requirement many U.S. allies in Europe and Asia worry could be increasingly difficult given the upcoming election and deteriorating situation in the Middle East and the demands the region is once again placing on U.S. officials. The Biden administration took important steps in 2023 to strengthen alliances and extended deterrence assurances to U.S. allies, and deepen planning and coordination on key crisis management issues. Finding ways to institutionalize and deepen these efforts will be critical. These efforts should focus on a range of possible conflict scenarios with Russia, China, and North Korea and dig into some hard questions: What specifically do various alliances intend to deter? Who would do what in a crisis? What might be perceived as escalatory? How would allies communicate with one another and the public during a contingency? How might various alliances might integrate conventional and nuclear operations during a crisis, or take certain actions to deter opportunistic aggression?

It will also be important to watch how Washington postures its nuclear forces over the next year to both assure allies and demonstrate its readiness and resolve to U.S. adversaries. The United States has shifted to a much more dynamic mode of messaging and communicating its nuclear force movements—from a significant uptick in bomber task force missions to a much more visible presence for U.S. ballistic missile submarines . Going forward, officials need to take a holistic look at what effect these measures have (and what the implications for future force management decisions might be) and find opportunities to monitor how certain actions or exercises in one theater register, or not, with adversaries in another.

• Progress on U.S. Nuclear Modernization

Finally, with such a dynamic threat environment, 2024 will be a critical year for the nuclear enterprise. Every major element of U.S. nuclear forces is being modernized. But delays, budget overruns , supply chain issues, and significant workforce and infrastructure constraints across both the defense and national lab sectors are leading to an increasing disconnect between policy debates over what might be needed in the future and the reality of what the existing workforce and infrastructure can support. This needs to change in 2024. Congress needs to change the way it oversees defense and National Nuclear Security Administration programs and work with the Pentagon to enact significant changes to the way the enterprise assesses risks—not just the risks of delays across the nuclear enterprise but also to conventional acquisition programs that are critical to our ability to deter, and prevail in, if necessary, a high-intensity conflict. To be clear, this is not just a resourcing issue. Service members will soon be operating both legacy and replacement systems concurrently—a challenge the U.S. Air Force and Navy have not encountered for decades. Managing these issues requires leadership and careful attention from the highest levels—a commodity that is often in short supply.

Unfortunately, these are far from the only challenges the United States and its allies will have to contend with in 2024. Washington will also have to manage the growing proxy war with Iran and ongoing concerns about its nuclear program, as well as a host of other nonproliferation challenges.

Thinking about the unthinkable in 2024 does not mean reviving Strangelovian concepts from the Cold War. Instead, it is about being realistic about the potential for direct conflicts with Russia, China, or North Korea and wrestling with a more difficult and uncomfortable question: If the United States goes to war, is it prepared to manage nuclear coercion and respond to potential nuclear use?

Kelsey Hartigan is deputy director of the Project on Nuclear Issues and senior fellow with the International Security Program at the Center for Strategic and International Studies in Washington, D.C.

Commentary is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).

© 2024 by the Center for Strategic and International Studies. All rights reserved.

Kelsey Hartigan

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Article contents

Nuclear weapons and international conflict: theories and empirical evidence.

• Daniel S. Geller Daniel S. Geller Daniel S. Geller is Professor and Chair of the Department of Political Science at Wayne State University. He conducts research and teaches in the areas of International Politics, Defense Policy, and Foreign Policy. From 2000 through 2010 Dr. Geller served as a consultant to the U.S. Department of State, Office of Technology and Assessments, and in 2009 he was a member of a Senior Advisory Group to the U.S. Strategic Command on the Nuclear Posture Review. Dr. Geller was a Co-Principal Investigator on an NSF grant involving the expansion of the militarized interstate dispute database. He has published extensively in books, journals and edited collections on the subject of interstate war. His most recent books are Nations at War: A Scientific Study of International Conflict (Cambridge University Press) co-authored with J. David Singer and The Construction and Cumulation of Knowledge in International Relations (Blackwell, Ltd.) co-edited with John A. Vasquez.
• https://doi.org/10.1093/acrefore/9780190228637.013.347
• Published online: 27 July 2017

The balance of conventional military capabilities is intrinsic to understanding patterns of war among nations. However, cumulative knowledge relating to the effects of nuclear weapons possession on conflict interaction is largely absent. Framework is provided for analyzing the results of quantitative empirical research on this question and to identify any extant strong and consistent patterns in the interactions of states that can be associated with the possession of nuclear weapons.

Since 1945, a vast, sophisticated, and contradictory literature has developed on the implications of nuclear weaponry for patterns of international conflict and war. This theoretical and empirical work has principally focused on the conflict effects of these weapons for the interaction of nuclear-armed states, although a growing number of studies have explored the impact of a state’s possession of nuclear weapons on the behavior of nonnuclear opponents. Given the destructive capacity of these weapons and their questionable value for battlefield use, most of this work has concentrated on the requirements for successful deterrence. In categorizing the studies, some scholars note that “classical deterrence theory” derives from the Realist paradigm of international politics and subdivide this theory into two complementary strands: structural (or neorealist) deterrence theory and decision-theoretic deterrence theory. In contrast, other analysts choose to classify work on nuclear deterrence into three schools of thought: nuclear irrelevance; risk manipulation, escalation, and limited war; and the nuclear revolution. The essence of these divisions involves a debate about what the possession of nuclear weapons does for a state that controls them. Does the possession of these weapons affect the behavior of nuclear and nonnuclear opponents in disputes over contested values? Do the weapons impart political influence and hold military utility, or are they useless as tools for deterrence, compellence, or war?

• nuclear weapons
• crisis escalation
• nuclear war
• international conflict
• empirical international relations theory

Introduction

The balance of conventional military capabilities is intrinsic to understanding patterns of war among nations (Geller, 2000a ). However, cumulative knowledge relating to the effects of nuclear weapons possession on conflict interaction is largely absent. This article seeks to provide a framework for analyzing the results of quantitative empirical research on this question and to identify any extant strong and consistent patterns in the interactions of states that can be associated with the possession of nuclear weapons.

Since 1945 , a vast, sophisticated, and contradictory literature has developed on the implications of nuclear weaponry for patterns of international conflict and war. 1 This theoretical and empirical work has principally focused on the conflict effects of these weapons for the interaction of nuclear-armed states, although a growing number of studies have explored the impact of a state’s possession of nuclear weapons on the behavior of nonnuclear opponents. Given the destructive capacity of these weapons and their questionable value for battlefield use, most of this work has concentrated on the requirements for successful deterrence. In categorizing the studies, Zagare and Kilgour ( 2000 ), for example, note that “classical deterrence theory” derives from the Realist paradigm of international politics, and they subdivide this theory into two complementary strands: structural (or neorealist) deterrence theory and decision-theoretic deterrence theory. In contrast, Jervis ( 1979 , 1984 , 1988 ), among others, chooses to classify work on nuclear deterrence into three schools of thought: nuclear irrelevance; risk manipulation, escalation, and limited war; and the nuclear revolution. The essence of these divisions involves a debate about what the possession of nuclear weapons does for a state that controls them. Does the possession of these weapons affect the behavior of nuclear and non-nuclear opponents in disputes over contested values? Do the weapons impart political influence and hold military utility or are they useless as tools for deterrence, compellence, or war?

Nuclear strategy has principally concerned itself with the efficacy of nuclear weapons as a deterrent. One school of thought—nuclear revolution theory—characterized by the works of Brodie ( 1946 , 1959 , 1978 ), Waltz ( 1981 , 1990 , 1993 , 2003 ), and Jervis ( 1984 , 1988 , 1989a ), holds that the incredibly rapid and destructive effects of nuclear weapons creates a strong disincentive for nuclear-armed states to engage each other in disputes that might escalate to the level of war. The “nuclear revolution” means that nuclear weapons can deter aggression at all levels of violence and makes confrontations and crises between nuclear-armed states rare events. The maintenance of a nuclear second-strike capability is all that is required for a successful military deterrent force.

A second school of thought—risk manipulation, escalation, and limited war—emphasizes the problem of “risk” in confrontations between states in possession of nuclear weapons. The issue here is that, in disputes between nuclear-armed states, the use of nuclear weapons carries such enormous costs for both sides that any threat to use the weapons lacks inherent credibility. While allowing that a nuclear second-strike capability can deter a full-scale nuclear strike by an opponent, these analysts argue that states will manipulate the risk of dispute escalation and war for the purposes of deterrence and compellence (e.g., Gray, 1979 ; Kahn, 1962 , 1965 ; Schelling, 1960 , 1966 ). In this view, crises and brinkmanship tactics become surrogates for war in confrontations between nations in possession of nuclear weapons (Snyder & Diesing, 1977 ). Associated with this thesis is the concept of the “stability-instability paradox” (Snyder, 1965 ), whereby nuclear-armed states are secure in the deterrence of general nuclear war but are free to exploit military asymmetries (including strategic and tactical nuclear asymmetries as well as conventional military advantages) at lower levels of violence (e.g., Kissinger, 1957 ).

Yet another perspective holds nuclear weapons to be “irrelevant” as special instruments of either statecraft or war (Mueller 1988 , 1989 ). 2 In this argument, nuclear weapons are not substantially different in their deterrent effect from conventional military forces and, in John Mueller’s view, developed nations will not engage each other in either conventional or nuclear wars—having already witnessed the devastation that can be produced with both types of weaponry. A related argument holds that the possession of nuclear weapons provides little or no coercive advantage in confrontations with either nuclear-armed or nonnuclear states. A number of quantitative empirical studies of deterrence failures and successes (in both direct- and extended-deterrence cases) have produced results supportive of this thesis. Additionally, a notable formal mathematical study of deterrence by Zagare and Kilgour ( 2000 ) demonstrates that raising the costs of war above a certain threshold has no effect on deterrence stability. In this work, Zagare and Kilgour also maintain that, while nuclear weapons may increase the costs associated with a deterrent threat, they simultaneously decrease the credibility of the threat—and hence the stability of deterrence. These contrary effects serve to minimize the impact of nuclear weapons on effective deterrence. In short, nuclear and nonnuclear crises should exhibit the same patterns of escalation.

Over the past 35 years, large-scale quantitative empirical studies have attempted to generate evidence relating to these theories. Discussion of some of these works follows.

Nuclear Weapons and Patterns of International Conflict

The nuclear revolution.

The term “nuclear revolution” was coined by Robert Jervis ( 1989a , ch. 1), although the initial recognition of the alterations in patterns of international politics likely to be wrought by nuclear weapons should be credited to Bernard Brodie ( 1946 ). As Jervis has noted:

the changes nuclear weapons have produced in world politics constitute a true revolution in the relationships between force and foreign policy. The fact that neither [the United States nor the Soviet Union] can protect itself without the other’s cooperation drastically alters the way in which force can be used or threatened . . . The result is to render much of our prenuclear logic inadequate. As Bernard Brodie has stressed, the first question to ask about a war is what the political goal is that justifies the military cost. When the cost is likely to be very high, only the most valuable goals are worth pursuing by military means . . . What prospective . . . goals could possibly justify the risk of total destruction? (Jervis, 1989a , p. 13, 24)

Moreover, for Jervis ( 1989b ), that this destruction was essentially unavoidable under any plausible strategy constituted the essence of the nuclear revolution. Jervis ( 1989a , pp. 23–25) went on to enumerate changes in international politics directly attributable to the presence of nuclear weaponry, including the absence of war among the great powers, the declining frequency of great power crises, and the tenuous link between the conventional or nuclear balance among great powers and the political outcomes of their disputes. 3

Kenneth Waltz ( 1981 , 1990 , 1993 , 2003 , 2008 ) has been exceptionally prominent in developing and forwarding the thesis that nuclear weapons are a force for peace and that nuclear proliferation will lead to declining frequencies of war. Waltz argues that nuclear weapons are simply more effective in dissuading states from engaging in war than are conventional weapons:

In a conventional world, states going to war can at once believe that they may win and that, should they lose, the price of defeat will be bearable (Waltz, 1990 , p. 743). A little reasoning leads to the conclusions that to fight nuclear wars is all but impossible and that to launch an offensive that might prompt nuclear retaliation is obvious folly. To reach these conclusions, complicated calculations are not required, only a little common sense (Waltz in Sagan & Waltz, 1995 , p. 113). The likelihood of war decreases as deterrent and defensive capabilities increase. Nuclear weapons make wars hard to start. These statements hold for small as for big nuclear powers. Because they do, the gradual spread of nuclear weapons is more to be welcomed than feared. (Waltz in Sagan & Waltz, 1995 , p. 45)

Given this logic, evidence consistent with an absence of war or the use of force short of war between nuclear-armed states and few (or a declining frequency of) crises between nuclear powers would be supportive of the nuclear revolution thesis.

Empirical Evidence

A number of quantitative empirical studies have produced evidence relevant to the nuclear revolution thesis. In an early study of the effects of nuclear weapons possession, Bueno de Mesquita and Riker ( 1982 ) present both a formal mathematical model and an empirical test of deterrence success. The model assumes the possibility of nuclear war (i.e., the use of nuclear weapons) when nuclear asymmetry exists (only one side possesses nuclear weapons), but assumes the absence of nuclear war among nuclear-armed states. The model indicates a rising probability of nuclear war resulting from nuclear proliferation to the midpoint of the international system, where half of the states possess nuclear weapons, at which point any further proliferation results in a declining probability of nuclear war. When all nations possess nuclear weapons, the probability of nuclear war is zero. The supporting empirical analysis uses early Correlates of War (COW) Project Militarized Interstate Dispute (MID) data, for the years 1945 through 1976 , for four classes of dyads: nuclear/nuclear, nuclear/nonnuclear with a nuclear ally, nuclear/nonnuclear, and nonnuclear/nonnuclear. The analysis examines the distribution of threats, interventions, and wars across the four dyad classes and indicates that the presence of a symmetric nuclear threat constrains conflict by reducing its likelihood of escalation to the level of war. The two classes of nuclear/nuclear and nuclear/nonnuclear with a nuclear ally have the highest probabilities of employing only threats and the lowest probabilities of engaging in interventions and wars. This evidence is consistent with the predictions of the nuclear revolution thesis. 4

Rauchhaus ( 2009 ) provides a multivariate analysis of factors associated with both militarized interstate disputes and wars for all dyads between 1885 and 2000 (MID database). The data set used in his study contains 611,310 dyad years, and tests were performed on time sections from 1885–1944 and 1945–2000 . He reports that in symmetric nuclear dyads (both states possess nuclear weapons) the odds of war drop precipitously. Rauchhaus concludes that Waltz and other nuclear revolution theorists find support for their thesis in the patterns uncovered by his study.

Asal and Beardsley ( 2007 ) examine the relationship between the severity of violence in international crises and the number of states involved in the crises that possess nuclear weapons. Using data from the International Crisis Behavior (ICB) Project for the years 1918 through 2000 , their results indicate that crises in which nuclear actors are involved are more likely to end without violence and that, as the number of nuclear-armed states engaged in crises increases, the probability of war decreases. This evidence is interpreted as supportive of the nuclear revolution thesis: the presence of nuclear weapon states in international crises has a violence-dampening effect due to the potential consequences of escalation and the use of nuclear force.

In a second study, Beardsley and Asal ( 2009a ) hypothesize that nuclear weapons act as shields against aggressive behavior directed toward their possessors. Specifically, it is postulated that nuclear states will be constrained in engaging in aggressive actions toward other nuclear-armed powers. Data is drawn from the ICB Project for the years 1945 through 2000 , using directed dyads as the unit of analysis. The results indicate that nuclear opponents of other nuclear-armed powers are limited in their use of violent force. However, Beardsley and Asal ( 2009a , p. 251) also note that the “restraining effect of nuclear weapons on violent aggression does not appear to affect the propensity for actors to engage each other in general crises, in contrast with the expectations of . . . the ‘nuclear revolution’ model. . .”

Additional results consistent with the nuclear revolution thesis are reported in a study by Sobek, Foster, and Robinson ( 2012 ). Using directed-dyad year with MID data for the period between 1945 and 2001 , the study examines the effects of efforts to develop nuclear weapons on the targeting of the proliferator in militarized disputes. Sobek et al. ( 2012 , p. 160) conclude that “. . .if a state . . . gains nuclear weapons, then the odds of being targeted in a militarized dispute falls.” States developing nuclear weapons are high-frequency targets in MIDs, but “. . .[t]argeting drops precipitously when [joint] acquisition is achieved” (Sobek et al., 2012 , p. 160).

However, Bell and Miller ( 2015 ) present evidence that is counter to the preceding studies. Using data collected by Rauchhaus ( 2009 ), they contend that nuclear dyads are neither more nor less likely to fight wars or engage in sub-war conflicts than are nonnuclear dyads. They argue that the evidence indicating a strong negative probability of war in symmetric nuclear dyads is due to the statistical model used by Rauchhaus, whereas the positive association for nuclear dyads and crisis frequency reported by Beardsley and Asal ( 2009a ) is due to selection effects (i.e., nuclear weapons possession is more a consequence rather than a cause of conflict).

The nuclear revolution thesis maintains that there should be a general absence of war or the use of force short of war among nuclear-armed states. In addition, there is the expectation of few (or a diminishing number of) crises in nuclear dyads, as the fear of escalation will exert a powerful constraint on aggressive behavior.

Bueno de Mesquita and Riker ( 1982 ) present compelling evidence that nuclear asymmetry or the absence of nuclear weapons on both sides of a conflict are more likely to be associated with war. In their data, between 1945 and 1976 , there were 17 cases of war between nonnuclear states, two cases of war in asymmetric nuclear dyads, and zero cases of war in either nuclear dyads or nuclear/nonnuclear dyads where the nonnuclear party had a nuclear-armed ally. Rauchhaus’s ( 2009 ) study also presents evidence that symmetric nuclear dyads are unlikely to engage in war. The article by Asal and Beardsley ( 2007 ) reports results consistent with those of Bueno de Mesquita and Riker ( 1982 ). Specifically, crises ending in war are not uncommon for confrontations engaging nonnuclear states and for confrontations in which only one state possesses nuclear weapons. However, as the number of nuclear participants increases beyond one, the probability of full-scale war diminishes. Only the results of Bell and Miller ( 2015 ) stand in contrast with the findings on symmetric nuclear dyads and the probability of war. Similarly, Beardsley and Asal ( 2009a ) show findings consistent with the nuclear revolution thesis: symmetric nuclear dyads engage in few crises where violence is the “preeminent” form of interaction. This conclusion is also supported by the findings reported by Sobek et al. ( 2012 ). However, Asal and Beardsley ( 2007 ) and Beardsley and Asal ( 2009a ) also note that there appears to be no constraining effect produced by nuclear weapons on the occurrence of crises that exhibit lower levels of hostility in symmetric nuclear dyads.

Since the advent of nuclear weapons in 1945 , there has been one war between nuclear-armed powers: the Kargil War of 1999 involving India and Pakistan (Geller, 2005 , p. 101). This conflict remained at the conventional level and surpassed the threshold of 1,000 battle deaths set by the Correlates of War Project for classification as a war (Singer & Small, 1972 ; Small & Singer, 1982 ). However, Paul ( 2005 , p. 13) argues that, despite the conventional military asymmetry between India and Pakistan (in India’s favor) that existed at the time of the Kargil War, the development of Pakistani nuclear weapons actually permitted Pakistan to launch a conventional invasion of the disputed territory of Kashmir. As Paul explains, only in a long war could India mobilize its material superiority, but as a result of the development of Pakistani nuclear weapons, a long war becomes “inconceivable” without incurring the risk of nuclear escalation. Hence, Pakistan’s leaders were emboldened to initiate a conventional war behind the shield of their nuclear deterrent despite their conventional military inferiority. This sole case of conventional war between nuclear-armed states—and its facilitation by the risk of unacceptable escalation provided by nuclear weapons—stands in stark contradiction to the predictions of nuclear revolution theory. 5

These collective results provide only partial support for the nuclear revolution thesis. As the theory suggests, war between nuclear-armed states should be nonexistent or a very rare event. This prediction, to date (with one notable exception), has been upheld. However, Beardsley and Asal ( 2009a ) report that symmetric nuclear dyads engage in an unexpectedly large number of crises—in contradiction to the predictions of nuclear revolution theory. This is an empirical question that will receive additional examination in the following section.

Risk Manipulation, Escalation, and Limited War

A second school of thought—risk manipulation, escalation, and limited war—finds its archetypal expression in the seminal work of Henry Kissinger ( 1957 ). According to this thesis (and counter to that of nuclear revolution theory), the possession of a nuclear second-strike capability may deter a nuclear attack by an opponent on one’s home territory, but not much else. Kissinger argued that the United States (and its NATO allies) required the ability to conduct successful combat operations at levels of violence below that of general nuclear war if the protection of Europe against Soviet aggression was a political goal. Some years later, Snyder ( 1965 ) discussed this as what was later termed the “stability-instability paradox.” The essence of the paradox was that stability at the level of general nuclear war permitted the exploitation of military asymmetries at lower levels of violence—including strategic (counterforce) and tactical nuclear wars as well as conventional forms of combat. The thesis that strategic nuclear weapons possessed little political or military utility other than deterring a nuclear attack on one’s home territory led to a number of works devoted to the analysis of tactics for coercive bargaining and limited war by Thomas Schelling ( 1960 , 1966 ), Herman Kahn ( 1960 , 1962 , 1965 ), and others. 6

As Snyder and Diesing ( 1977 , p. 450) maintain, the primary effect of the possession of nuclear weapons on the behavior of nuclear adversaries is the creation of new constraints on the ultimate range of their coercive tactics—a result of the extraordinary increase in the interval between the value of the interests at stake in a conflict and the potential costs of war. They note that before the advent of nuclear weapons, this interval was comparatively small and states could more readily accept the risk of war in a coercive bargaining crisis or engage in war in order to avoid the loss of a contested value. In contradistinction, given even small numbers of nuclear weapons in the stockpiles of states, it is far more difficult to conceive of an issue worth incurring the high risk of nuclear war, much less the cost of actually fighting one. 7

According to this thesis, a direct result of the constraints created by the presence of nuclear weapons has been the attempt by nuclear powers to control, in a more finely calibrated manner, the threat and application of force in disputes with other nuclear-armed states. These developments find theoretical and empirical expression in the concept of escalation , which is defined as the sequential expansion of the scope or intensity of conflict (Osgood & Tucker, 1967 , p. 127, 188). 8 In most standard formulations, escalation is conceived as a generally “controllable and reversible process,” 9 which a rational decision maker can employ in conflict situations as an instrument of state policy (Osgood & Tucker, 1967 , p. 188). Decision makers estimate the relative bargaining power of the rivals and engage in increasingly coercive tactics that are designed to undermine the opponent’s resolve. Controlled escalation occurs when each side is capable of inflicting major or unacceptable damage on the other but avoids this while attempting to influence the opponent with measured increases in the conflict level that incorporate the threat of possible continued expansion.

The measured application of force and the ability to control escalation in nuclear disputes are seen—by these strategic theorists—as indispensable for securing political values while minimizing risk and cost (Osgood & Tucker, 1967 , p. 137; Russett, 1988 , p. 284). A preeminent theorist in this school, Herman Kahn ( 1965 , p. 3), described escalation as “an increase in the level of conflict . . . [often assuming the form of] a competition in risk-taking or . . . resolve.” As this theory developed, conflict analysts elaborated the risks involved in the process and incorporated the manipulation of these risks as a possible tactic in one’s strategy. 10

Clearly, nuclear weapons have not altered the values at stake in interstate disputes (and the desire to avoid political loss), but rather have increased the rapid and immediate costs of war. As a result, in a severe conflict between nuclear powers, the decision maker’s dilemma is to construct a strategy to secure political interests through coercive actions that raise the possibility of war without pushing the risk to an intolerable level. Some analysts argue that the solution to this problem has entailed an increase in the “threshold of provocation,” providing greater area of coercive maneuver in the threat, display, and limited use of force (Osgood & Tucker, 1967 , pp. 144–145; Snyder & Diesing, 1977 , p. 451). Hostile interaction between nuclear powers under this higher provocation threshold can range from verbal threats and warnings, to military deployments and displays, to the use of force in limited wars. Hence, in disputes between nuclear powers, it is argued that military force should be viewed as requisite but “potentially catastrophic power” that must be carefully managed and controlled within the bounds of reciprocally recognized constraints (Osgood & Tucker 1967 , p. 137).

It is frequently stated that the principal exemplar of this new form of competition is the local crisis. Obviously, crises have an extensive history in international politics, but the argument is made that the nuclear age has produced an expansion of steps on the escalation ladder and has intensified the maneuvering of nuclear rivals for dominant position in conflicts below the level of all-out war. For example, Snyder and Diesing note that:

the expanded range of crisis tactics in the nuclear era can be linked to a new conception of crises as surrogates for war, rather than merely dangerous incidents that might lead to war. . . [S]ince war is no longer a plausible option between nuclear powers, they have turned to threats of force and the demonstrative use of force short of war as a means of getting their way. The winner of the encounter is the one who can appear the most resolved to take risks and stand up to risks. (Snyder & Diesing, 1977 , pp. 455–456)

Given this logic, conflicts between nuclear powers should reveal different escalatory patterns than conflicts between states where only one side possesses nuclear arms, or conflicts where neither side possesses nuclear arms. Specifically, disputes between nuclear powers should evidence a greater tendency to escalate—short of war—than nonnuclear disputes or disputes, in which only one side possesses a nuclear capability.

Kugler ( 1984 ) presents an empirical test of classical nuclear deterrence theory: the study examines whether nuclear weapons are salient in preventing the initiation or escalation of war to extreme levels. The analysis focuses on crisis interactions involving the United States, the Soviet Union, and China (PRC) with the case set drawn from Butterworth ( 1976 ) and CACI (Mahoney & Clayberg, 1978 , 1979 ). The cases used in the analysis constitute 14 extreme crises where nuclear nations were involved and where nuclear weapons “played a central role” (Kugler, 1984 , p. 477). The results indicate that crises of extreme intensity diminish as the threat of nuclear devastation becomes mutual. In other words, as the capacity of actors to destroy each other with nuclear weapons increases, there is a tendency to decrease the intensity of conflict, and to settle those crises that reach extreme proportions by compromise. This suggests that deterrence of war through the symmetric possession of nuclear weapons is operative in the conflict dynamics of great-power crises.

As Siverson and Miller ( 1993 , pp. 86–87) note, the earliest systematic statistical work on the effect of nuclear weapons possession in the escalation of conflict is by Geller ( 1990 ). This study employs the Correlates of War (COW) Militarized Interstate Dispute (MID) data covering 393 MIDs between 1946 and 1976 and uses the MID five-level dispute hostility index in coding the dependent variable. The results indicate that dispute escalation probabilities are significantly affected by the distribution of nuclear capabilities. Comparing the escalatory behavior of nuclear dyads with the escalatory behavior of nonnuclear dyads in militarized disputes, it is reported that symmetric nuclear disputes indicate a far greater tendency to escalate—short of war—than do disputes for nonnuclear pairs: disputes in which both parties possess nuclear weapons have approximately a seven times greater probability (0.238) of escalating of escalating than do disputes in which neither party possesses nuclear arms (0.032). The conclusion indicates that the presence of nuclear weapons impacts the crisis behavior of states, with disputes between nuclear states more likely to escalate, short of war, than disputes between nonnuclear nations.

Huth, Gelpi, and Bennett ( 1993 ) analyze 97 cases of great power deterrence encounters from 1816 to 1984 as a means of testing the explanatory power of two competing theoretical approaches to dispute escalation. Dispute escalation is defined as the failure of the deterrent policies of the defender. Deterrence failure occurs when the confrontation ends in either the large-scale use of force or defender capitulation to the challenger’s demands. For the post- 1945 period, the findings indicate that, for nuclear dyads, the possession of a nuclear second-strike capability by the defender substantially reduces the likelihood of the confrontation ending either in war or in capitulation by the defender. However, the possession of nuclear weapons in great power dyads does not deter the challenger from initiating militarized disputes.

Asal and Beardsley ( 2007 ) examine the relationship between the severity of violence in crises and the number of states involved in the confrontations that possess nuclear weapons. Using data from the International Crisis Behavior (ICB) Project, the study includes 434 international crises extending from 1918 through 2001 . The results indicate that symmetric nuclear dyads engage in an unexpectedly large number of crises—and that “crises involving nuclear actors are more likely to end without violence. . . [A]s the number of nuclear actors increases, the likelihood of war continues to fall” (Asal & Beardsley, 2007 , p. 140). The authors also note that their results indicate that there may be competing effects within nuclear dyads: specifically, that both sides will avoid war but engage in sub-war levels of escalatory behavior (Asal & Beardsley 2007 , p. 150, fn. 6).

Rauchhaus ( 2009 ) also attempts to test the effects of nuclear weapons possession on conflict behavior. The data are generated using the EUGene (v.3.203) statistical package for dyad years from 1885 through 2000 and for a subset period from 1946 through 2000 . 11 The findings indicate that, in militarized disputes, symmetric nuclear dyads have a lower probability of war than do dyads where only one nation possesses nuclear arms. Moreover, in dyads where there are nuclear weapons available on both sides (nuclear pairs), the findings indicate that disputes are associated with higher probabilities of crises and the use of force (below the level of war). The author suggests that the results support the implications of Snyder’s ( 1965 ) stability-instability paradox. The results are also supportive of the Snyder and Diesing ( 1977 ) contention that crises have become surrogates for war between nuclear-armed states where the manipulation of risk through coercive tactics is employed to secure political objectives.

A study by Kroenig ( 2013 ) provides similar results. Using an original data set of 52 nuclear crisis dyads drawn from the International Crisis Behavior Project for the years 1945 through 2001 , Kroenig codes the outcomes of nuclear crises against nuclear arsenal size and delivery vehicles, and the balance of political stakes in the crisis. He concludes “. . . that nuclear crises are competitions in risk taking, but that nuclear superiority—defined as an advantage in the size of a state’s nuclear arsenal relative to that of its opponent—increases the level of risk that a state is willing to run” (Kroenig, 2013 , p. 143), and hence its probability of winning the dispute without violence. These results support the contention that crises between nuclear-armed states tend to involve dangerous tactics of brinkmanship and tests of resolve.

Evidence consistent with the risk manipulation, escalation, and limited war thesis would include the presence of severe crises between nuclear powers that exhibit escalatory behavior short of unconstrained war but inclusive of the use of force. The limited conventional war of 1999 between India and Pakistan, initiated and carried out by Pakistan under the umbrella of its nuclear deterrent, is an extreme example of precisely this type of conflict interaction. It captures the logic of Snyder’s stability-instability paradox and incorporates, as well, descriptions by Schelling and by Kahn of the use of limited war (with the risk of greater violence to follow) as a means of persuading an adversary to relinquish a contested value.

Beardsley and Asal ( 2009a ) report that symmetric nuclear dyads engage in an unexpectedly large number of crises—a finding that is consistent with the Snyder and Diesing ( 1977 ) contention that crises have become surrogates for war among nuclear-armed states. Similarly, Huth, Bennett, and Gelpi ( 1992 ) note that, in great-power dyads, the possession of nuclear weapons by the defender does not deter dispute initiation by a nuclear-armed challenger, and that an outcome of either war or capitulation by the defender is unlikely. In findings not inconsistent with those of Huth et al., ( 1992 ), Kugler ( 1984 ) reports that (between 1946 and 1981 ), as the capacity of nuclear actors to destroy each other increases, there is a tendency to decrease the intensity of the conflict. Both Geller ( 1990 ) and Rauchhaus ( 2009 ), in large-scale quantitative empirical analyses of escalation patterns in nuclear, nonnuclear, and mixed (asymmetric) dyads, report that symmetric nuclear dyads are substantially more likely to escalate dispute hostility levels—short of war—than are nonnuclear pairs of states. In Geller’s study, the findings indicate that disputes in which both parties possessed nuclear weapons had approximately a seven times greater probability of escalation (0.238) than did disputes in which neither party possessed nuclear arms (0.032). Last, Kroenig ( 2013 ) demonstrates that confrontations between nuclear-armed states may be understood as competitions in risk taking and that an advantage in the size of one’s nuclear arsenal is associated with increased levels of risk acceptance and, hence, successful coercion.

These cumulative findings are strongly supportive of the risk manipulation, escalation, and limited war thesis on the effects of symmetric nuclear weapons possession. 12 Moreover, the case of the 1999 limited conventional war between India and Pakistan reflects both the logic of this school of thought as well as the patterns of escalation described in the large-scale quantitative studies of militarized disputes between nuclear-armed states.

Nuclear Irrelevance

The views of John Mueller are most commonly associated with the thesis of “nuclear irrelevance.” Mueller ( 1988 , 1989 ) makes the highly controversial argument that nuclear weapons neither defined the stability of the post-Second World War U.S.-Soviet relationship nor prevented a war between the superpowers; he also maintains that the weapons did not determine alliance patterns or induce caution in U.S.-Soviet crisis behavior. His contention is that the postwar world would have developed in the same manner even if nuclear weapons did not exist.

Mueller’s logic allows that a nuclear war would be catastrophic, but that nuclear weapons simply reinforced a military reality that had been made all too clear by World War II: even conventional war between great powers is too destructive to serve any conceivable political purpose. Moreover, the satisfaction with the status quo shared by the United States and the Soviet Union removed any desire for territorial conquest that might have led to conflict, as each superpower held dominance in its respective sphere of influence. Similarly, provocative crisis behavior was restrained by the fear of escalation—and although the presence of nuclear weapons may have embellished such caution, the mere possibility of fighting another conventional war such as World War II would have induced fear and restraint on the part of decision makers. In short, nuclear weapons may have enhanced Cold War stability, but their absence would not have produced a different world. Mueller closes his argument with the extrapolation that war among developed nations is obsolescent. It may simply be that, in the developed world, a conviction has grown that war among post-industrial states “would be intolerably costly, unwise, futile, and debased” (Mueller, 1988 , p. 78). In this sense, nuclear weapons lack deterrent value among developed states because—absent the incentive for war—there is nothing to deter.

In a related thesis, Vasquez ( 1991 ) holds that it is unlikely—given what is known about the complex conjunction of multiple factors in the steps to war—that any single factor, such as the availability of nuclear weapons, causes or prevents wars. He makes the nuanced argument, in discussing the long post-war peace between the United States and the Soviet Union, that:

There is little evidence to support the claim that nuclear deterrence has prevented nuclear war or that it could do so in the future, if severely tested . . . Nuclear war may have been prevented not because of deterrence, but because those factors pushing the United States and the USSR toward war have not been sufficiently great to override the risks and costs of total war (Vasquez, 1991 , p. 207, 214).

Of principal significance to Vasquez is the absence of a direct territorial dispute between the superpowers. Other factors that Vasquez believes contributed to the long peace include satisfaction with the status quo, the experience of the two world wars, the establishment of rules and norms of interaction between the superpowers, procedures for crisis management, and effective arms control regimes. 13

A second area of application for the nuclear irrelevancy thesis involves asymmetric dyads. Little has been written about the effects of nuclear weapons on the patterns of serious disputes where this technology is possessed by only one side. However, what has been written suggests that in these types of conflicts nuclear weaponry may lack both military and psychological salience. For example, Osgood and Tucker ( 1967 , p. 158) and Blainey ( 1973 , p. 201) argue that tactical nuclear weapons are largely devoid of military significance in either Third World conflicts or insurgencies, where suitable targets for the weapons are absent. An additional disincentive to the use of nuclear weapons against a nonnuclear opponent is that it might be expected to increase the pressures for nuclear proliferation and to incite international criticism and denunciation of the nuclear state (Huth, 1988a , p. 428). It also has been suggested that a sense of fairness or proportionality contributes a moral aspect to the practical military and political inhibitions on using nuclear weapons against a nonnuclear opponent and that the set of these concerns has undermined the efficacy of nuclear power as a deterrent in asymmetric conflicts (Huth & Russett, 1988 , p. 38; Russett, 1989 , p. 184).

Moreover, Waltz ( 1967 , p. 222) and Osgood and Tucker ( 1967 , pp. 162–163) caution against exaggerating the differences due to nuclear weapons between contemporary and historical major power-minor power conflicts. Long before the advent of nuclear weapons, minor powers frequently defied or withstood great power pressure as a result of circumstances of geography, alliance, or an intensity of interests that the major power could not match.

In a similar argument, Jervis ( 1984 , p. 132) examines the logic of escalation in a losing cause (presumably a tactic relating directly to disputes between nuclear and nonnuclear states) and suggests that a threat to fight a war that almost certainly would be lost may not be without credibility—indeed, there may be compelling reasons for actually engaging in such a conflict. Specifically, if the cost of winning the war is higher to the major power than is the value at stake in the dispute, then the confrontation embodies the game structure of “Chicken.” Hence, even if war is more damaging to the minor power than to the major power, the stronger may still prefer capitulation or a compromise solution to the confrontation rather than engaging in the fight. In sum, Jervis ( 1984 , p. 135) argues that: “the ability to tolerate and raise the level of risk is not closely tied to military superiority . . . The links between military power—both local and global—and states' behavior in crises are thus tenuous.”

The third area of application for the nuclear irrelevancy thesis involves policies of extended deterrence. The efficacy of nuclear weapons for the purposes of extended deterrence was an issue of immense importance throughout the Cold War. In fact, the positions on whether American strategic nuclear weapons were sufficient to deter a Soviet-Warsaw Pact invasion of Western Europe or whether substantial conventional and tactical nuclear weapons were necessary for successful deterrence constituted a continuing debate for decades. Nuclear revolution theory contended that the U.S. strategic nuclear arsenal (with its ability to destroy the Soviet Union) was sufficient to induce caution and restraint on the part of the Soviet leadership. However, the strategists who formulated the stability-instability paradox argued that U.S. strategic nuclear weapons would deter a direct nuclear strike on the United States itself, but little else. According to this logic, for the successful extended deterrence of an attack on Europe, the United States and NATO required effective combat forces that could fight at the level of conventional war and even war with tactical nuclear weapons. Escalation dominance was required to sustain extended deterrence. Of course, extended deterrence policies existed long before the development of nuclear weapons and applied to any situation where a powerful defender attempted to deter an attack against an ally by threat of military response. The issue at hand is the effectiveness of a strategic nuclear threat in sustaining a successful extended deterrence policy. The nuclear irrelevancy position is that such weapons lack significance in extended deterrence situations.

In sum, the nuclear irrelevance thesis suggests that nuclear weapons have little salience in the interaction patterns of nuclear-armed dyads. Evidence consistent with this position would indicate that, for symmetric dyads, the possession of nuclear weapons or the nuclear balance does not affect crisis escalation, crisis outcomes, or dispute initiation patterns. In addition, if a set of practical, political, and ethical constraints has weakened the military advantage of possessing nuclear weapons in a serious dispute with a nonnuclear state, then the monopolization of a nuclear capability will not confer a bargaining edge to the nuclear-armed state in an asymmetric crisis. The nuclear irrelevance school would also gain support in findings indicating the absence of substantive effects resulting from possession of nuclear weapons in extended deterrence situations.

In evaluating the empirical evidence regarding the nuclear irrelevance thesis, it is useful analytically to separate the studies into distinct categories: (a) findings involving the effects of nuclear weapons in nuclear-armed dyads; (b) findings involving the interaction patterns of nuclear-armed states against nonnuclear opponents; and (c) findings bearing on extended deterrence situations.

(a) Nuclear dyads . The examination of evidence relating to nuclear revolution theory upheld the prediction that, as the theory suggests, war between nuclear-armed states should be nonexistent or a very rare event (e.g., Asal & Beardsley, 2007 ; Bueno de Mesquita & Riker, 1982 ; Rauchhaus, 2009 ). The success of this prediction (with the exception of the 1999 Kargil War) serves as the principal finding in support of the nuclear revolution thesis. However, this finding holds negative implications for the validity of the nuclear irrelevancy thesis. In other findings counter to the patterns hypothesized by the nuclear irrelevancy thesis, Geller ( 1990 ) reports results that indicate that the distribution of nuclear capabilities affects the patterns of escalation in militarized interstate disputes, and that symmetric nuclear dyads show substantially higher dispute escalation probabilities, short of war, than do nonnuclear dyads. Rauchhaus’s ( 2009 ) findings mirror Geller’s. Similarly, Beardsley and Asal ( 2009a ) note that the crisis behavior of symmetric nuclear dyads differs from that of asymmetric dyads. Only the work of Bell and Miller ( 2015 ) stands in opposition to this general pattern. Using data from Rauchhaus ( 2009 ), Bell and Miller ( 2015 , p. 83) contend that nuclear dyads do not exhibit conflict patterns distinct from nonnuclear dyads either in terms of war or sub-war militarized disputes.

However, other evidence relating to conflict behavior, crisis interaction patterns, or crisis outcomes that indicate that nuclear weapons were inconsequential in the disputes would support the contention that nuclear forces are irrelevant in symmetric dyads. For example, Blechman and Kaplan ( 1978 ) provide an empirical analysis of 215 incidents between 1946 and 1975 , in which the United States used its armed forces for political objectives. Their findings indicate that the strategic nuclear weapons balance between the United States and the Soviet Union did not influence the outcome of competitive incidents involving the two states (Blechman & Kaplan, 1978 , pp. 127–129). Instead, the authors maintain that the local balance of conventional military power was more important in determining the outcomes of the confrontations (Blechman & Kaplan, 1978 , p. 527).

Kugler ( 1984 ) presents an empirical test of nuclear deterrence theory by examining whether nuclear weapons are efficacious in preventing the initiation or escalation of crises to the level of war. The case set is 14 extreme crises between 1946 and 1981 involving the United States, the Soviet Union, and China. Of the 14 crises, five involved nuclear-armed dyads (a nuclear power on each side). He concludes that: “nuclear nations do not have an obvious and direct advantage over other nuclear . . . nations in extreme crises. Rather, conventional [military] capabilities are the best predictor of outcome of extreme crises regardless of their severity” (Kugler, 1984 , p.501).

In contrast to the findings by Blechman and Kaplan ( 1978 ) and Kugler ( 1984 ), a study by Kroenig ( 2013 ) provides different results. Using a data set of 52 nuclear crisis dyads ( 1945–2001 ) drawn from the International Crisis Behavior (ICB) Project, Kroenig codes the outcomes of nuclear crises, nuclear arsenal size and delivery vehicles, and the balance of political stakes in the crisis. He concludes that nuclear superiority—defined as an advantage in the size of a state’s nuclear arsenal relative to that of its opponent—increases the level of risk that a state is willing to run and hence its probability of winning the dispute without violence (Kroenig, 2013 , p. 143).

Huth et al. ( 1992 ) examine militarized dispute-initiation patterns among great power rivalries between 1816 and 1975 as a means of testing a set of explanatory variables drawn from multiple levels of analysis. The principal focus of the study is to investigate the relationship between the structure of the international system and the initiation of great power disputes. However, the analysis does include a variable coded for the possession of nuclear weapons by the challenger’s rival. The findings indicate that the presence of defenders’ nuclear weapons does not deter challengers from initiating militarized disputes among great powers (Huth et al., 1992 , p. 478, 513).

Gartzke and Jo ( 2009 ) examine the effects of nuclear weapons possession on patterns of militarized dispute initiation using a sophisticated multivariate model and data drawn from the COW/MID database for directed dyads over the years 1946 through 2001 . Their findings indicate that nuclear weapons possession has little effect on dispute initiation behavior. The authors note that: “Instead, countries with security problems, greater interest in international affairs, or significant military capabilities are simultaneously more likely to fight and proliferate” (Gartzke & Jo, 2009 , p. 221). The relationship between nuclear weapons and MID initiation is rejected statistically: this finding applies to both symmetric (nuclear) and asymmetric (nuclear/nonnuclear) dyads.

(b) Asymmetric dyads . The nuclear irrelevancy school also maintains that the possession of nuclear weapons confers no bargaining advantage on the nuclear-armed power engaged in a confrontation with a nonnuclear state.

In a seminal study examining the effects of nuclear weapons on conflict interaction patterns, Organski and Kugler ( 1980 , pp. 163–164) identify 14 deterrence cases that occurred between 1945 and 1979 in which nuclear weapons could have been used. Seven of these cases involved a nuclear power in confrontation with a nonnuclear state (or a state with an ineffective nuclear force ). Their findings indicate that in only one case out of the seven did the nuclear-armed state win: “Nonnuclear powers defied, attacked, and defeated nuclear powers and got away with it” (Organski & Kugler, 1980 , p. 176). In the six cases that the nuclear power lost to a nonnuclear state, the winner was estimated to have conventional military superiority at the site of the confrontation (Organski & Kugler, 1980 , p. 177).

In a related study, Kugler ( 1984 ) isolates 14 cases of extreme crisis that occurred between 1946 and 1981 , in which nuclear weapons were available to at least one party in the dispute. Of these 14 cases, nine involved confrontations in which only one state had access to nuclear arms. In all nine cases, the outcomes of the crises favored the nonnuclear challenger. Once again, the balance of conventional military capabilities—not nuclear weaponry—provided the best predictor of crisis outcome (Kugler, 1984 , p. 501).

In an early large-scale study, Geller ( 1990 ) examines conflict escalation patterns in serious interstate disputes among nations with both symmetric and asymmetric types of weapons technology. This study employs the Correlates of War (COW) Militarized Interstate Dispute (MID) data, inclusive of 393 MIDs between 1946 and 1976 , and uses the MID five-level dispute hostility index in coding the dependent variable. The findings indicate that, for asymmetric dyads (with only one state in possession of nuclear arms), the availability of nuclear force has no evident inhibitory effect on the escalation propensities of nonnuclear opponents. In fact, the findings show that in this class of confrontation, both nonnuclear dispute initiators and targets act more aggressively than do their nuclear-armed opponents. The summation suggests that in confrontations between nuclear and nonnuclear states, war is a distinct possibility, with aggressive escalation by the nonnuclear power probable. In such cases, it is concluded that the conventional military balance may be determinative of the outcome (Geller, 1990 , p. 307).

In two studies published in 1994 and 1995 , Paul employs the case study method to examine the dynamics of asymmetric war initiation by weaker powers. Paul ( 1994 ) analyzes six cases of war initiation by weaker states against stronger states: three of these cases (China/U.S. in 1950 ; Egypt/Israel in 1973 ; and Argentina/Great Britain in 1982 ) involve nonnuclear nations initiating wars against nuclear-armed opponents. Paul ( 1994 , p. 173) concludes that nuclear weapons appear to have limited utility in averting war in asymmetric dyads. He notes that, with either nuclear or conventional weapons, a significant military advantage may be insufficient to deter a weaker state that is highly motivated to change the status quo. In a more focused study, Paul ( 1995 ) discusses the possible reasons underlying the nonuse of nuclear weapons by nuclear-armed states against nonnuclear opponents. Here he analyzes two cases (Argentina/Great Britain in the Falklands War of 1982 and Egypt/Israel in the Middle East War of 1973 ) in which nonnuclear states initiated wars against nuclear opponents. Paul argues that in both cases nuclear retaliation by the targets was deemed highly improbable by the nonnuclear war initiators due to a combination of limited war goals and taboos (unwritten and uncodified prohibitionary norms) against the use of nuclear weapons.

Rauchhaus ( 2009 ) attempts to test the effects of nuclear weapons possession on conflict behavior for asymmetric as well as for symmetric dyads using data generated by the EUGene (v.3.203) statistical program for dyad years from 1885 through 2000 . The findings indicate that, for asymmetric (nuclear/nonnuclear) dyads (in comparison to symmetric dyads), there is a higher probability of war. Asymmetric dyads are also more likely to be involved in militarized disputes that reach the level of the use of force (Rauchhaus, 2009 , pp. 269–270). In short, the study produces results that hold in opposition to the view that conflict between nuclear and nonnuclear states will be limited. As Rauchhaus ( 2009 , p. 271) concludes: “nuclear asymmetry is generally associated with a higher chance of crises, uses of force, fatalities, and war.”

A study by Beardsley and Asal ( 2009b ) produces findings that stand in counterpoint to the main body of analyses on conflict in asymmetric dyads. This work examines the question of whether the possession of nuclear weapons affects the probability of prevailing in a crisis. The data are drawn from the International Crisis Behavior (ICB) Project for directed dyads covering the years between 1945 and 2002 . The findings indicate that the possession of nuclear weapons provides bargaining leverage against nonnuclear opponents in crises: nuclear actors are more likely to prevail when facing a nonnuclear state (Beardsley & Asal, 2009b , p. 278, 289).

However, with regard to bargaining advantages that may be derived from the possession of nuclear weapons, Sechser and Fuhrmann ( 2013 ) argue (counter to Beardsley & Asal) that compellent threats based on nuclear force may lack credibility due to their indiscriminately destructive effects and the reputational costs that, presumably, would be associated with their use. Drawing on a new data set (Militarized Compellent Threats) containing 242 challenger-target dyads for the period 1918 to 2001 , they report findings indicating that “states possessing nuclear weapons are not more likely to make successful compellent threats [than nonnuclear states] . . . and that nuclear weapons carry little weight as tools of compellence” (Sechser & Fuhrmann, 2013 , p. 174).

An interesting corollary finding is presented by Narang ( 2013 ). Using data collected by Bennett and Stam ( 2004 ) to explore the conflict behavior of regional (non-superpower) nuclear actors from 1945 through 2001 , Narang finds little evidence supporting an existential deterrent effect for nuclear weapons against nonnuclear opponents. Rather, he concludes that the nuclear posture adopted by the nuclear-armed state is determinative of deterrence success, with an “asymmetric escalation” posture superior to either a “catalytic” or “assured destruction” posture in deterring conventional attacks with military force (Narang, 2013 , p. 280, 284–286).

(c) Extended deterrence . The logic of the nuclear irrelevancy thesis suggests that nuclear weapons should be of little salience in extended deterrence situations.

Huth defines deterrence as a policy that seeks to convince an adversary through threat of military retaliation that the costs of using military force outweigh any expected benefits. Extended deterrence is then defined by Huth ( 1988a , p. 424) as a confrontation between a defender and a potential attacker in which the defender threatens the use of military force against the potential attacker’s use of force against an ally (protégé) of the defender. There have been a large number of studies produced on the issue of the efficacy of extended nuclear deterrence—the majority of which report a body of consistent or complementary findings.

As noted in Harvey and James ( 1992 ), Bruce Russett’s ( 1963 ) analysis of 17 crises that occurred between 1935 and 1961 appears to be the first aggregate study of the factors associated with extended deterrence success and failure. Nine crisis cases involved defenders with a nuclear capability, and six of the nine cases resulted in successful extended deterrence. However, Russett draws no conclusions as to the independent effect of nuclear weapons on those outcomes. He does note that military equality on either the local (conventional) or strategic (nuclear) level appears to be a necessary condition for extended deterrence success.

Two studies published by Weede ( 1981 , 1983 ) also deal with the effectiveness of extended nuclear deterrence. Weede examines 299 dyads between 1962 and 1980 for evidence relating to patterns of extended deterrence success or failure. His findings are supportive of the position that nuclear weapons assist in producing extended deterrence success.

In a subsequent study, Huth and Russett ( 1984 ) increased the size of Russett’s ( 1963 ) sample set from 17 to 54 historical cases of extended deterrence from 1900 through 1980 . The findings indicate that the effect of nuclear weapons on extended deterrence success or failure is marginal. Of much greater import are the combined local conventional military capabilities of the defender and protégé; hence, conventional, rather than nuclear, combat power is associated with the probability of extended deterrence success.

In two related studies, Huth ( 1988a , 1988b ) examines 58 historical cases of extended deterrence and reports findings similar to those found in Huth and Russett ( 1984 ). Specifically, the possession of nuclear weapons by the defender did not have a statistically significant effect on deterrence outcomes when the target itself was a nonnuclear power. In addition, the ability of the defender to deny the potential attacker a quick and decisive conventional military victory on the battlefield was correlated with extended deterrence success.

Huth and Russett ( 1988 ) present an analysis of Huth’s ( 1988b ) 58 historical cases of extended deterrence success and failure. In this database, there were 16 cases of extended deterrence crises where defenders possessed nuclear weapons. The findings indicate that a defender’s nuclear capability was essentially irrelevant to extended deterrence outcomes; existing and locally superior conventional military forces were of much greater importance to deterrence success.

Huth ( 1990 ) produced another study based on the data set described in his 1988b book. In this study, he examines the effects of the possession of nuclear weapons by a defender only in extended deterrent crises not characterized by mutual assured destruction (i.e., where the potential attacker either does not possess nuclear weapons or does not possess a significant nuclear capability). He reports that, when the defender has an advantage in conventional forces, nuclear weapons do not play a significant role in the outcomes of extended deterrence confrontations (Huth, 1990 , p. 271).

In an unusual work, Carlson ( 1998 ) combines a formal mathematical model with an empirical test of escalation in extended deterrence crises. Using Huth’s ( 1988b ) data extending from 1885 to 1983 , the analysis examines the 58 cases of extended deterrence crises. Measures include the estimated cost-tolerance of both attackers and defenders. The findings indicate that low cost-tolerance challengers are less likely to escalate a crisis to higher levels of hostility when the defender possesses nuclear weapons.

Fuhrmann and Sechser ( 2014 ) report findings similar to those of Weede ( 1981 , 1983 ) and Carlson ( 1998 ), insofar as the independent extended deterrent effect of nuclear weapons is supported. Using Militarized Interstate Dispute (MID) data for the years 1950 through 2000 , and controlling for the effects of contiguity, polity-type of challenger, power ratio, and nuclear status of challenger, they conclude that “formal defense pacts with nuclear states have significant deterrence benefits. Having a nuclear-armed ally is strongly associated with a lower likelihood of being targeted in a violent militarized dispute . . .” (Fuhrmann & Sechser, 2014 , p. 920).

The empirical evidence regarding the nuclear irrelevance thesis has been divided analytically into three distinct categories: (a) findings involving the effect of nuclear weapons in nuclear dyads; (b) findings involving the interaction patterns of nuclear-armed states against nonnuclear opponents; and (c) findings relating to extended deterrence situations.

Regarding Category “a”—the effect of nuclear weapons on conflict patterns in nuclear dyads—the results are mixed. According to the logic of the nuclear irrelevancy thesis, nuclear-armed dyads should show identical conflict patterns to nonnuclear dyads. This prediction is supported by the findings of Bell and Miller ( 2015 ). However, Asal and Beardsley ( 2007 ), Bueno de Mesquita and Riker ( 1982 ), and Rauchhaus ( 2009 ) all note that empirical probabilities of war are far lower for nuclear dyads than for nonnuclear dyads. Moreover, Geller ( 1990 ) reports results indicating that the distribution of nuclear capabilities affects escalation patterns in militarized interstate disputes, and that symmetric nuclear dyads show substantially higher dispute escalation probabilities—short of war—than do nonnuclear dyads. Rauchhaus’s ( 2009 ) findings are identical to Geller’s. Similarly, Beardsley and Asal ( 2009a ) note that the crisis behavior of symmetric nuclear dyads differs from that of asymmetric dyads. In sum, contrary to the predictions of the nuclear irrelevancy school, these findings suggest that patterns of war and crisis escalation differ among symmetric nuclear dyads, asymmetric dyads, and nonnuclear dyads.

Nevertheless, there is a body of evidence for nuclear dyads that supports the nuclear irrelevancy thesis; these findings focus on the effects of the nuclear balance on crisis outcomes and the effect of nuclear weapons on patterns of dispute initiation. Both Blechman and Kaplan ( 1978 ; with 215 incidents from 1946 to 1975 ) and Kugler ( 1984 ; five extreme crises between 1946 and 1981 ), report that the balance of nuclear forces in nuclear dyads was less significant in influencing the outcome of confrontations than was the local balance of conventional military capabilities. Only Kroenig’s ( 2013 ) work indicates a crisis bargaining advantage accruing to a state with nuclear superiority in symmetric nuclear dyads. With regard to dispute initiation, Huth et al. ( 1992 ) report a lack of salience regarding the availability of nuclear weapons for great powers and the initiation patterns of their militarized disputes. Gartzke and Jo ( 2009 ) similarly note that nuclear weapons show no statistically significant relationship to the initiation of militarized interstate disputes in either symmetric or asymmetric dyads. In sum, the findings of this subset of studies are consistent with the thrust of the nuclear irrelevancy thesis regarding both the effects of the nuclear balance on crisis outcomes and the effects of the availability of nuclear weapons on dispute initiation patterns.

Category “b”—focusing on the interaction patterns of nuclear-armed states against nonnuclear opponents—provides a second set of cumulative findings. Organski and Kugler ( 1980 ), Kugler ( 1984 ), Geller ( 1990 ), and Rauchhaus ( 2009 ) all conclude that the possession of nuclear weapons provides little leverage in the conflict patterns or outcomes of disputes in asymmetric dyads. Organski and Kugler ( 1980 ) note that, in six cases out of seven, nonnuclear states achieved their objectives in confrontations with nuclear-armed states. Kugler ( 1984 ) reports that in nine crises between nuclear and nonnuclear states, the outcomes in every case favored the nonnuclear party. In both studies, conventional military capabilities at the site of the confrontation provided the best predictor of crisis outcome.

Geller’s ( 1990 ) analysis indicates that in 34 asymmetric disputes with a nuclear initiator, the nonnuclear target matched or escalated the initiator’s hostility level in 24 cases (71%); in 56 asymmetric disputes with a nonnuclear initiator, the nuclear target deescalated the crisis by failing to match or exceed the nonnuclear initiator’s hostility level in 35 cases (63%). Moreover, 35 of the total of 90 cases (39%) of asymmetric disputes reached the level in which force was used. These findings show that in this class of dyad, nonnuclear dispute initiators as well as targets act more aggressively than do their nuclear-armed opponents. The conclusion suggests that in confrontations between nuclear and nonnuclear states, the use of force, including war, is a distinct possibility, with aggressive escalation by the nonnuclear state probable. In such cases of asymmetric distribution of nuclear forces, the conventional military balance may well be the determinative factor in the outcome of the dispute.

The findings of Rauchhaus ( 2009 ) reinforce those discussed above: there is a higher probability of war in asymmetric dyads than in symmetric nuclear dyads, and asymmetric dyads are more likely than symmetric nuclear dyads to experience militarized disputes that engage the use of force. As Rauchhaus concludes, nuclear asymmetry is associated with higher probabilities of crises, limited use of force, and war, than are symmetric nuclear dyads.

A study by Narang ( 2013 ) offers corollary evidence that the deterrent effect of the possession of nuclear weapons (for regional nuclear powers engaged in disputes with nonnuclear states) depends heavily on the nuclear posture that is adopted. Specifically, in contrast to catalytic or assured destruction postures, only an asymmetric escalation posture has any effect in deterring conventional military assaults. Last, Sechser and Fuhrmann ( 2013 ) report findings indicating that, although nuclear weapons may provide deterrent value, they are irrelevant as instruments of compellence.

These results are generally consistent with the predictions of the nuclear irrelevance thesis regarding conflict patterns in asymmetric dyads: the possession of nuclear weapons confers little or no advantage to nuclear-armed states in disputes with nonnuclear opponents. Paul’s ( 1994 , 1995 ) case studies of instances of war initiation by nonnuclear states against nuclear-armed adversaries offer additional evidence in conformity with this pattern.

In sum, the findings of this subset of studies are supportive of the thrust of the nuclear irrelevance thesis regarding both the effects of the nuclear balance on crisis outcomes and the effects of nuclear weapons possession on dispute initiation patterns: the possession of nuclear weapons does not impede aggressive behavior by nonnuclear states.

Category “c”—extended deterrence crises—also provides a pattern of results. Studies by Huth and Russett ( 1984 , 1988 ), and Huth ( 1988a , 1988b , 1990 ) report the essential irrelevance of a defender’s possession of nuclear weapons to extended deterrence success. These studies indicate that existing and locally superior conventional military force is the factor most frequently associated with the majority of successful extended deterrence outcomes. Russett ( 1963 ) notes the ambiguous effects of a nuclear capability in situations of extended deterrence and concludes that military equality on either the conventional or nuclear level appears to be minimally requisite for extended deterrence success. However, Weede ( 1981 , 1983 ), Carlson ( 1998 ), and Fuhrmann and Sechser ( 2014 ) report evidence contrary to the general set of findings: specifically, that nuclear weapons assist in producing successful outcomes in extended deterrence situations.

In sum, the cumulative findings in all three areas are consistent with some of the predictions of the nuclear irrelevance school and inconsistent with others. For symmetric nuclear dyads, a substantial set of findings indicates that patterns of war and crisis escalation differ between symmetric nuclear dyads, asymmetric dyads, and nonnuclear dyads. Counter to the predictions of the nuclear irrelevancy thesis, nuclear weapons affect the nature of conflict interaction between nuclear-armed states. At the same time, there is a subset of findings consistent with the predictions of nuclear irrelevancy for nuclear dyads: the nuclear balance does not affect the outcome of crises (the balance of local conventional military forces is more important), nor does the symmetric possession of nuclear weapons distinguish initiation patterns of militarized disputes from initiation patterns in asymmetric or nonnuclear disputes. Also supportive of the irrelevancy thesis are findings indicating that, for asymmetric dyads, the possession of nuclear arms provides scant advantage in crises and confrontations with nonnuclear states. Escalation by the nonnuclear adversary and its use of force—including war—are outcomes with surprisingly high probabilities. Last, in extended deterrence situations, the cumulative findings tend toward the essential irrelevance of nuclear weapons possession and point instead toward the salience of the local balance of conventional military forces in determining crisis outcomes.

This article has reviewed the three principal schools of thought regarding the effects of nuclear weapons possession on patterns of international conflict: (a) nuclear revolution theory; (b) risk manipulation, escalation, and limited war; and (c) nuclear irrelevance. Quantitative empirical works that produced findings relevant to evaluating the predictions of these schools were then collated by category and their results compared to the predictions.

For nuclear revolution theory, the findings offer limited, but not insignificant, support. For example, as predicted, wars among nuclear-armed states have been rare events. To date, with the exception of India and Pakistan in 1999 , no other militarized dispute between nuclear powers has reached the level of war (based on Correlates of War Project coding rules). As Waltz and Jervis have predicted, wars occur among nuclear-armed states at a far lower proportional frequency than in asymmetric or nonnuclear dyads. However, the prediction of nuclear revolution theory—that there will be few crises among nuclear-armed powers—has not been supported by the quantitative empirical evidence. Similarly, the prediction that those crises that do develop among nuclear powers will be settled rapidly and without serious escalation has not found empirical support.

For the risk manipulation, escalation, and limited war school, the evidence has proved more uniformly favorable. The prediction by Snyder and Diesing ( 1977 ) that crises among nuclear-armed states will be used as surrogates for war—with associated tactics (including the limited use of force) designed to increase risk and intimidate through dangerous escalatory behaviors—has been largely supported. Comparisons of crisis escalation probabilities between symmetric nuclear dyads, asymmetric dyads, and nonnuclear dyads clearly show higher escalation probabilities for nuclear dyads than for the other two classes, with disputes for nuclear dyads approximately seven times more likely to escalate—short of war—than disputes for nonnuclear dyads. Moreover, the case of the 1999 war between India and Pakistan conforms to the logic of Snyder’s stability-instability paradox whereby limited war is fought between nuclear powers under the protective umbrellas of their nuclear deterrents.

The nuclear irrelevance school, like nuclear revolution theory, finds mixed support in the extant empirical evidence. The nuclear irrelevancy thesis can be categorized according to predictions involving (a) the effects of nuclear weapons in nuclear dyads, (b) the effects of nuclear weapons possession in asymmetric dyads, and (c) the effects of nuclear weapons in extended deterrence situations. Counter to the logic of this school, cumulative empirical evidence indicates that nuclear weapons do make a difference in certain types of conflict interaction. Patterns of war and crisis escalation differ between symmetric nuclear dyads, asymmetric dyads, and nonnuclear dyads, with nuclear dyads less likely to fight wars and more likely to exhibit crisis escalation patterns short of war than nonnuclear dyads.

Supportive of the contentions of the nuclear irrelevancy school are findings indicating that in asymmetric dyads, the possession of nuclear arms provides no discernable advantage in crises and confrontations. Escalation by the nonnuclear adversary and its use of force against its nuclear-armed opponent—including war—are distinct outcomes with surprisingly high probabilities. Lastly, in extended deterrence situations, the cumulative findings indicate the essential irrelevance of nuclear weapons possession and point instead toward the salience of the local balance of conventional military forces in determining outcomes.

Three conclusions may be drawn from the patterns discussed above.

Wars among nuclear-armed states are improbable. If confrontations do escalate to the level of violence, such violence will likely remain conventional. Hence, the spread of nuclear weapons increasingly supports the maintenance of the status quo.

Crises among nuclear powers have a higher probability of escalating—short of war—than do crises for asymmetric or nonnuclear dyads. It is apparent that symmetric nuclear dyads engage in dangerous tactics involving the manipulation of risk as a means of securing policy, objectives.

In asymmetric dyads the possession of nuclear weapons does not impede aggressive behavior by a nonnuclear adversary. Hence, the advantage in holding nuclear weaponry does not translate into bargaining leverage in confrontations between nuclear states and their nonnuclear adversaries.

It is evident that the effects of nuclear weapons possession on patterns of international conflict are complex. Moreover, the patterns themselves may be subject to change as a result of events. For example, the future use of nuclear weapons in a war between nuclear-armed states or the use of such weapons in a war against a nonnuclear state might lead to different expectations of outcomes and thereby alter the subsequent strategic calculations and policy choices of decision makers. Unmistakably, nuclear weapons have raised the prompt and potential long-term costs of war. Empirical analysis has indicated in what way these weapons have affected the patterns of international conflict in the past. How these weapons may ultimately affect the future conflict patterns of states remains to be determined.

Acknowledgment

I wish to thank John Vasquez, Jack Levy, and Peter Wallensteen for their expert commentaries on an earlier version of this article. This article is an expanded and revised version of Daniel S. Geller (2012), Nuclear Weapons and War, in J. A. Vasquez (Ed.), What Do We Know About War? (2d ed.). Used by permission of Rowman & Littlefield Publishing Group. All rights reserved.

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1. See Gartzke and Kroenig ( 2016 ) for an excellent review of this literature. Related studies that examine the determinants of nuclear proliferation include Meyer ( 1984 ), Sagan ( 1996/1997 ), Geller ( 2003 ), Singh and Way ( 2004 ), Hymans ( 2006 , 2012 ), Solingen ( 2007 , 2012 ), Jo and Gartzke ( 2007 ), Gartzke and Kroenig ( 2009 ), Kroenig ( 2009 , 2010 ), Fuhrmann ( 2009 ), Horowitz ( 2010 ), Bleek ( 2010 ), Bleek and Lorber ( 2014 ), Brown and Kaplow ( 2014 ), Miller ( 2014 ), Way and Weeks ( 2014 ), and Reiter ( 2014 ).

2. As Mueller ( 1988 , pp. 55–56) notes: “nuclear weapons neither define a fundamental stability nor threaten severely to disturb it. . . [W]hile nuclear weapons may have substantially influenced political rhetoric, public discourse, and defense budgets and planning, it is not at all clear that they have had a significant impact on the history of world affairs since World War II.”

3. Others attributing to nuclear weapons causal significance for the “long peace” between the United States and the Soviet Union include The Harvard Nuclear Study Group ( 1983 ), Tucker ( 1985 ), Quester ( 1986 ), Bundy ( 1988 ), and Gaddis ( 1991 ). However, Levy ( 1989 , pp. 289–295), while noting the stability in the superpower relationship produced by nuclear weapons, cautions about pressures for preemptive war that may develop between nuclear-armed states.

4. Intriligator and Brito ( 1981 ) present a similar formal mathematical analysis of the effects of nuclear proliferation on the probability of nuclear war—but in this case without associated empirical data. The mathematical model demonstrates that the effects of nuclear proliferation on the probability of nuclear war depend on the number of existing nuclear weapon states, and that proliferation may reduce rather than increase the probability of nuclear war. Once two or more states achieve a secure second-strike capability, the addition of new nuclear states decreases the incentive to initiate a nuclear war. However, Intriligator and Brito note that, while the probability of a calculated nuclear attack may decrease as a result of proliferation, there may be an increase in the probability of accidental or irrational nuclear war as these weapons spread throughout the system.

5. For a different interpretation of the 1999 Kargil War—by Waltz—see Sagan and Waltz ( 2003 , pp. 109–124). Also see Basrur ( 2007–2008 ) and Diehl, Goertz, and Saeedi ( 2005 ) for analyses suggesting, like Waltz, that caution was imposed in the conduct of the Kargil War by nuclear weapons. For a sophisticated model of the effects of various levels of nuclear war between India and Pakistan, see Batcher ( 2004 ).

6. Major works, many using formal mathematical models, that explore the factors associated with deterrence, brinkmanship and the manipulation of risk, crisis stability, threat credibility, and the consequences of nuclear proliferation include those by Ellsberg (1959[ 1968 ], 1960 ), Brams and Kilgour ( 1985 ), Powell ( 1987 , 1988 ), Kugler ( 1987 ), Nalebuff ( 1988 ), Langlois ( 1991 ), Wagner ( 1991 ), Carlson ( 1995 ), Brito and Intriligator ( 1996 ), Zagare and Kilgour ( 2000 ), Danilovic ( 2002 ), Morgan ( 1977 , 2003 ), and Zagare ( 2007 ).

7. For example, see Bundy and Blight ( 1987–1988 , pp. 30–92). Glaser and Fetter ( 2016 ), in a sophisticated analysis of potential United States damage-limitation strategies and forces vis-à-vis China, conclude that such an effort would most likely fail and would undermine a stable deterrence relationship. Indeed, Mueller ( 1988 , 1989 ) presents an argument that, among developed countries, major war (nuclear or conventional) is no longer considered a realistic foreign policy option due to the massive destructive effects. But Mueller ( 1988 , p. 56) also contends that nuclear weapons have not fundamentally affected the crisis behavior of major powers. For a response to this argument, see Jervis ( 1988 ).

8. Escalation theory is a subset of the more general body of theory on strategic interaction in international politics (e.g., Singer, 1963 ).

9. Strategic theorists fully recognize, however, that escalation of conflict can occur irrespective of the desires of the participants due to factors of miscalculation or momentum. This possibility—and an appreciation of it—forms a key element in the work of some theorists in this school (e.g., Schelling, 1966 , ch. 3).

10. Other early works with sections on escalation that touch on the subject of risk are Kahn ( 1962 , ch. 6), Snyder ( 1961 , pp. 252–258), Schelling ( 1966 , pp. 99–116, 166–168), Schelling ( 1960 , appendix A), and Halperin ( 1963 , chs. 1–2, 4). The issue of “costly signals” with regard to the credibility of threats and commitments are elaborations on the themes of these early studies on escalation (e.g., Fearon, 1994a , 1994b , 1997 ; Schultz, 1998 ). For example, Fearon ( 1997 , p. 82) discusses the relative merits of the “tie-hands” and “sink-cost” signaling strategies. Fearon demonstrates (using formal methods) that costly signals are more successful if they involve a tie-hands strategy (create costs that would be paid ex post if they fail to uphold the commitment) rather than if a sink-cost strategy is pursued (which is only costly to the actor ex ante). The tie-hands strategy is connected to ex post domestic audience costs. The model also indicates that decision makers will not bluff with either type of costly signal; they will not incur or create costs and then fail to carry out the threat.

11. Rauchhaus notes that the analysis performed on the second data set covering only the years 1946 through 2000 (when nuclear weapons were available) did not produce different statistical or substantive results in comparisons between patterns of nuclear and nonnuclear disputes using the 1885–2000 database.

12. In an interesting study at the monadic level, Grieco ( 2012 ) conducts a comparative analysis of the conflict behavior of states before and after the acquisition of nuclear weapons. His principal finding is that states do not become more prone to the initiation of military crises after acquiring nuclear weapons.

13. In a more recent work, Vasquez (Senese & Vasquez, 2008 ) allows that nuclear weapons have raised the provocation threshold for total war: “What would have provoked a war between major states in the pre-nuclear era no longer does so” (Senese & Vasquez, 2008 , p. 62). Nevertheless, Vasquez ( 2009 ) continues to maintain that a proper evaluation of the effects of nuclear weapons on war is within the context of the “steps to war” model (e.g., Senese & Vasquez, 2008 ; Vasquez, 1993 ). For an alternative explanation of war based on a process of complex conjunctive causation see Geller and Singer ( 1998 ) and Geller ( 2000b , 2004 , 2005 ).

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Annual Review of Political Science

Volume 19, 2016, review article, nukes with numbers: empirical research on the consequences of nuclear weapons for international conflict.

• Erik Gartzke 1,2 , and Matthew Kroenig 3
• View Affiliations Hide Affiliations Affiliations: 1 Department of Political Science, University of California San Diego, La Jolla, California 92093; email: [email protected] 2 School of International and Public Affairs, Columbia University, New York, New York 10027 3 Department of Government and School of Foreign Service, Georgetown University, Washington, DC 20057; email: [email protected]
• Vol. 19:397-412 (Volume publication date May 2016) https://doi.org/10.1146/annurev-polisci-110113-122130
• First published as a Review in Advance on March 02, 2016
• © Annual Reviews

Research on nuclear security has gone quantitative. Rapid growth in empirical approaches to the consequences of nuclear weapons in recent years promises to settle some controversies, even as it initiates or resurrects debates that may eventually be resolved with better estimates or data. The toolkit for studying nuclear security had long been bereft of quantitative approaches, undermining the virtuous cycle between theory and evidence. New data and growing confidence in statistical approaches have finally produced a systematic empirical literature on the consequences of nuclear weapons. We review existing studies, organizing the literature along thematic lines. We also discuss challenges facing the emergent quantitative literature and suggest several avenues for future research. Although the terminus of the basic research agenda has been anticipated more than once, the literature on nuclear consequences has shown a remarkable ability to generate novel and often unexpected research questions.

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What is a nuclear weapon?

A nuclear weapon is a device designed to release energy in an explosive manner as a result of nuclear fission, nuclear fusion, or a combination of the two processes.

Are there treaties to control the proliferation of nuclear weapons?

Concerns about the devastating effects of nuclear weapons have driven governments to negotiate arms control agreements. Some of the earliest ones include the Nuclear Test-Ban Treaty of 1963 and the Treaty on the Non-proliferation of Nuclear Weapons of 1968.

When was a nuclear weapon first tested?

The first test of a nuclear weapon occurred in the United States on July 16, 1945, at the Alamogordo Bombing Range in south-central New Mexico. The test was code-named Trinity.

The Soviet Union had the most nuclear weapons during the Cold War. The Soviet stockpile reached a peak of about 33,000 operational warheads in 1988, with an additional 10,000 previously deployed warheads that had been retired but not dismantled. The U.S. stockpile reached its peak in 1966 with more than 32,000 nuclear warheads.

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nuclear weapon , device designed to release energy in an explosive manner as a result of nuclear fission , nuclear fusion , or a combination of the two processes. Fission weapons are commonly referred to as atomic bombs . Fusion weapons are also referred to as thermonuclear bombs or, more commonly, hydrogen bombs; they are usually defined as nuclear weapons in which at least a portion of the energy is released by nuclear fusion.

Nuclear weapons produce enormous explosive energy. Their significance may best be appreciated by the coining of the words kiloton (1,000 tons) and megaton (1,000,000 tons) to describe their blast energy in equivalent weights of the conventional chemical explosive TNT . For example, the atomic bomb dropped on Hiroshima , Japan , in 1945, containing only about 64 kg (140 pounds) of highly enriched uranium , released energy equaling about 15 kilotons of chemical explosive. That blast immediately produced a strong shock wave , enormous amounts of heat, and lethal ionizing radiation . Convection currents created by the explosion drew dust and other debris into the air, creating the mushroom-shaped cloud that has since become the virtual signature of a nuclear explosion. In addition, radioactive debris was carried by winds high into the atmosphere, later to settle to Earth as radioactive fallout . The enormous toll in destruction, death, injury, and sickness produced by the explosions at Hiroshima and, three days later, at Nagasaki was on a scale never before produced by any single weapon . In the decades since 1945, even as many countries have developed nuclear weapons of far greater strength than those used against the Japanese cities, concerns about the dreadful effects of such weapons have driven governments to negotiate arms control agreements, such as the Nuclear Test-Ban Treaty of 1963 and the Treaty on the Non-proliferation of Nuclear Weapons of 1968. Among military strategists and planners, the very presence of these weapons of unparalleled destructive power has created a distinct discipline , with its own internal logic and set of doctrines, known as nuclear strategy .

The first nuclear weapons were bombs delivered by aircraft. Later, warheads were developed for strategic ballistic missiles, which have become by far the most important nuclear weapons. Smaller tactical nuclear weapons have also been developed, including ones for artillery projectiles, land mines , antisubmarine depth charges , torpedoes , and shorter-range ballistic and cruise missiles .

By far the greatest force driving the development of nuclear weapons after World War II (though not by any means the only force) was the Cold War confrontation that pitted the United States and its allies against the Soviet Union and its satellite states. During this period, which lasted roughly from 1945 to 1991, the American stockpile of nuclear weapons reached its peak in 1966, with more than 32,000 warheads of 30 different types. During the 1990s, following the dissolution of the Soviet Union and the end of the Cold War, many types of tactical and strategic weapons were retired and dismantled to comply with arms control negotiations, such as the Strategic Arms Reduction Talks , or as unilateral initiatives . By 2010 the United States had approximately 9,400 warheads of nine types, including two types of bombs, three types for intercontinental ballistic missiles (ICBMs), two types for submarine-launched ballistic missiles (SLBMs), and two types for cruise missiles . Some types existed in several modifications. Of these 9,400 warheads, an estimated 2,468 were operational (that is, mated to a delivery system such as a missile); the rest were either spares held in reserve or retired warheads scheduled to be dismantled. Of the 2,468 operational warheads, approximately 1,968 were deployed on strategic (long-range) delivery systems, and some 500 were deployed on nonstrategic (short-range) systems. Of the 500 nonstrategic warheads in the U.S. arsenal, about 200 were deployed in Europe.

The Soviet nuclear stockpile reached its peak of about 33,000 operational warheads in 1988, with an additional 10,000 previously deployed warheads that had been retired but had not been taken apart. After the disintegration of the Soviet Union, Russia accelerated its warhead dismantlement program, but the status of many of the 12,000 warheads estimated to remain in its stockpile in 2010 was unclear. Given limited Russian resources and lack of legitimate military missions, only about 4,600 of these 12,000 warheads were serviceable and maintained enough to be deployed. Of the 4,600 operational warheads, some 2,600 were deployed on strategic systems and some 2,000 on nonstrategic systems. A global security concern is the safety of Russia ’s intact warheads and the security of nuclear materials removed from dismantled warheads.

Beginning in the 1990s, the arsenals of the United Kingdom , France , and China also underwent significant change and consolidation. Britain eliminated its land-based army, tactical naval, and air nuclear missions, so that its arsenal, which contained some 350 warheads in the 1970s, had just 225 warheads in 2010. Of these, fewer than 160 were operational, all on its ballistic missile submarine fleet. Meanwhile, France reduced its arsenal from some 540 operational warheads at the end of the Cold War to about 300 in 2010, eliminating several types of nuclear weapon systems. The Chinese stockpile remained fairly steady during the 1990s and then started to grow at the beginning of the 21st century. By 2010 China had about 240 warheads in its stockpile, some 180 of them operational and the rest in reserve or retirement.

Israel maintained an undeclared nuclear stockpile of 60 to 80 warheads, but any developments were kept highly secret. India was estimated to have 60 to 80 assembled warheads and Pakistan about 70 to 90. Most of India’s and Pakistan’s warheads were thought not to be operational, though both countries—rivals in the incipient arms race on the Indian subcontinent—were thought to be increasing their stockpiles. North Korea , which joined the nuclear club in 2006, may have produced enough plutonium by 2010 for as many as 8 to 12 warheads, though it was not clear that any of these was operational.

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• 04 August 2020

Researchers: help free the world of nuclear weapons

You have full access to this article via your institution.

Hiroshima survivor Setsuko Thurlow (pictured, centre, receiving the 2017 Nobel Peace Prize on behalf of the International Campaign to Abolish Nuclear Weapons) has written to world leaders this week urging them to step up disarmament efforts. Credit: Lise Aserud/EPA-EFE/Shutterstock

The start of August marks an inauspicious anniversary for science, that of the first — and, so far, only — use of nuclear weapons in war.

Seventy-five years have passed since the bombing of the Japanese cities of Hiroshima and Nagasaki, on 6 and 9 August 1945, which killed in the region of 200,000 people. The risk of nuclear conflict remains, and nuclear weapons exist in alarmingly large quantities. At present, the world’s nuclear arsenal — 90% of which is in the United States and Russia — includes an estimated 1,335 tonnes of highly enriched uranium and 13,410 warheads.

The generation of scientists that created nuclear weapons carried with them a heavy burden of responsibility.Some would go on to become committed disarmament campaigners. Others helped to shape a series of important conferences and agreements, starting with the 1970 Treaty on the Non-Proliferation of Nuclear Weapons (NPT), whose aims include preventing non-nuclear-armed countries from developing or acquiring weapons technology.

But 50 years of nuclear diplomacy has made one thing clear: the nuclear nations are not ready to give up their weapons just yet. Progress has been made in reducing stockpiles, but these countries are simultaneously investing in updating their arsenals to last well into this century.

So what could persuade the United States, Russia, France, the United Kingdom, China, India, Pakistan, Israel and North Korea to begin fully dismantling their stocks, and to agree never again to develop nuclear weapons?

One idea, which has been in gestation for some years, could be about to have its break-out moment. A new agreement, the Treaty on the Prohibition of Nuclear Weapons (TPNW), is expected to become international law next year — and scientists have a chance to play a part in helping it to succeed.

Nuclear weapons: arms-control efforts need China

An urgent task will be to establish a new global network of researchers with knowledge on different aspects of nuclear science and technology. The treaty has yet to establish a formal scientific advisory mechanism. Some research groups, notably the Program on Science and Global Security at Princeton University in New Jersey, have been advising the treaty’s founders on various facets of nuclear science, such as how to accurately verify that stockpiles have been permanently dismantled 1 . But a more-permanent arrangement, whereby researchers from different countries can offer — and respond to requests for — advice will be needed. Because relations between Russia and the United States have worsened, the many formal and informal networks of nuclear scientists that once existed between these countries are now “practically non-existent”, says former US energy secretary Ernest Moniz, co-chair of the Nuclear Threat Initiative, a think tank based in Washington DC. A new global network will be essential to ensuring the safety of nuclear arsenals, because a lack of communication increases the chance of accidents and misunderstandings, heightening the risk of nuclear weapons being used.

Breakneck progress

The TPNW was agreed in 2017 by 122 non-nuclear countries, mostly in the global south, but also including two European Union member states. The strategy in creating this treaty was conceived a decade earlier by researchers and campaigners at the Acronym Institute for Disarmament Diplomacy in London; the Australian affiliate of International Physicians for the Prevention of Nuclear War; the Women’s International League for Peace and Freedom, based in Geneva, Switzerland, and New York City; and Japan’s Hibakusha, the survivors of the 1945 nuclear attacks.

Together, they built a larger coalition called the International Campaign to Abolish Nuclear Weapons (ICAN), and worked with scientists, United Nations diplomats and humanitarian organizations such as the Red Cross 2 . Some 40 countries have already incorporated the treaty into their national laws, and processes are under way for this to happen in more national parliaments.

Once 50 countries have signed it into law, the TPNW will have the status of an international law. At that point, it will become difficult for individuals (including scientists), as well as companies (including banks), from the treaty’s member countries to play any part in the development and deployment of nuclear-weapons technologies, says Rebecca Johnson at the Acronym Institute, who is one of the architects of the new treaty. But scientists who work on disarmament technologies will not be affected — they are much needed.

The treaty came about for a number of reasons. To begin with, the non-nuclear nations realized that they had to find a way to influence nuclear policy from beyond the shadow of the nuclear states. There seemed to be little justice in countries with nuclear weapons being the ones to decide the rules for the majority who wish for a nuclear-free world.

How a small nuclear war would transform the entire planet

Representatives of the bigger nuclear powers have often argued that they have earnt the right to be the world’s nuclear guardians, because they are stable countries with the most advanced nuclear science and technology — both essential ingredients in ensuring that stockpiles are safe and secure. But, in recent years, the argument that these countries can be trusted to look after the security interests of the rest of the world has become less credible.

Non-nuclear countries have grown increasingly alarmed as, in 2018, the United States withdrew from the Joint Comprehensive Plan of Action, also known as the Iran nuclear deal, and, in 2019, the United States and Russia suspended the Intermediate-Range Nuclear Forces Treaty .

And so, in addition to working with the existing nuclear agreements — in which the nuclear states have a veto — non-nuclear countries negotiated the new treaty through the United Nations General Assembly, under which every country has one vote.

At the same time, the non-nuclear states were able to boost their cause by drawing on some of the latest findings from researchers studying a potential ‘nuclear winter’ — the severe global cooling predicted to follow a nuclear war . Recent research has shown that a relatively small nuclear war between India and Pakistan could cause crops to fail in dozens of countries, devastating food supplies for more than one billion people 3 . Other research reveals that a nuclear winter would drastically alter ocean chemistry and cause serious harm to reefs and other marine ecosystems 4 .

Crucially, the treaty’s designers deliberately organized the preparatory process so that female researchers and diplomats were present in significant numbers — which is not usually the case in existing nuclear agreements. As a result of this commitment to knowledge, equality and diplomacy, ICAN was awarded the 2017 Nobel Peace Prize.

A new centre of gravity

The big question is to what extent the TPNW will make a difference to the actions of nuclear states. None has signed, but they will all be affected, in part because the treaty prohibits companies and individuals from signatory countries from assisting in weapons development. And because the TPNW is an intergovernmental agreement, nuclear-weapons countries will need to send delegates to its meetings, whether or not they agree with it.

The TPNW is a historic achievement with a lot riding on its young shoulders. It will still take decades to achieve a weapons-free world, but every journey needs to begin somewhere. Altering the balance of decision-making so that it is shared more equally between the nuclear states and the international community is that necessary first step.

Nature 584 , 7 (2020)

doi: https://doi.org/10.1038/d41586-020-02274-9

Philippe, S., Goldston, R. J., Glaser, A. & d’Errico, F. Nature Commun. 7 , 12890 (2016).

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Johnson, R. in Nuclear Disarmament: A Critical Assessment (eds Nikolas, B., Steen, V. & Njølstad, O.) 75–93 (Routledge, 2019).

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Nuclear weapons: Why reducing the risk of nuclear war should be a key concern of our generation

The consequences of nuclear war would be devastating. much more should – and can – be done to reduce the risk that humanity will ever fight such a war..

The shockwave and heat that the detonation of a single nuclear weapon creates can end the lives of millions of people immediately.

But even larger is the devastation that would follow a nuclear war.

The first reason for this is nuclear fallout. Radioactive dust from the detonating bombs rises up into the atmosphere and spreads out over large areas of the world from where it falls down and causes deadly levels of radiation.

The second reason is less widely known. But this consequence – 'nuclear winter' and the worldwide famine that would follow – is now believed to be the most serious consequence of nuclear war.

Cities that are attacked by nuclear missiles burn at such an intensity that they create their own wind system, a firestorm: hot air above the burning city ascends and is replaced by air that rushes in from all directions. The storm-force winds fan the flames and create immense heat.

From this firestorm, large columns of smoke and soot rise up above the burning cities and travel all the way up to the stratosphere. There it spreads around the planet and blocks the sun’s light. At that great height – far above the clouds – it cannot be rained out, meaning that it will remain there for years, darkening the sky and thereby drying and chilling the planet.

The nuclear winter that would follow a large-scale nuclear war is expected to lead to temperature declines of 20 or even 30 degrees Celsius (60–86° F) in many of the world’s agricultural regions – including much of Eurasia and North America. Nuclear winter would cause a 'nuclear famine'. The world’s food production would fail and billions of people would starve. 1

These consequences – nuclear fallout and nuclear winter leading to famine – mean that the destruction caused by nuclear weapons is not contained to the battlefield. It would not just harm the attacked country. Nuclear war would devastate all countries, including the attacker.

The possibility of global devastation is what makes the prospect of nuclear war so very terrifying. And it is also why nuclear weapons are so unattractive for warfare. A weapon that can lead to self-destruction is not a weapon that can be used strategically.

US President Reagan put it in clear words at the height of the Cold War: “A nuclear war cannot be won and must never be fought. The only value in our two nations possessing nuclear weapons is to make sure they will never be used. But then would it not be better to do away with them entirely?” 2

Nuclear stockpiles have been reduced, but the risk remains high

40 years after Reagan’s words, the Cold War is over and nuclear stockpiles have been reduced considerably, as the chart shows.

The world has learned that nuclear armament is not the one-way street that it was once believed to be. Disarmament is possible.

But the chart also shows that there are still almost ten thousand nuclear weapons distributed among nine countries on our planet, at least. 3 Each of these weapons can cause enormous destruction; many are much larger than the ones that the US dropped on Hiroshima and Nagasaki. 4

Collectively these weapons are immensely destructive. The nuclear winter scenario outlined above would kill billions of people— billions— in the years that follow a large-scale nuclear war, even if it was fought “only” with today’s reduced stockpiles. 5

It is unclear whether humanity as a species could possibly survive a full-scale nuclear war with the current stockpiles. 6 A nuclear war might well be humanity’s final war.

Close Calls: Instances that threatened to push the ‘balance of terror’ out of balance and into war

The ‘balance of terror’ is the idea that all involved political leaders are so scared of nuclear war that they never launch a nuclear attack.

If this is achievable at all, it can only be achieved if all nuclear powers keep their weapons in check. This is because the balance is vulnerable to accidents: a nuclear bomb that detonates accidentally – or even just a false alarm, with no weapons even involved – can trigger nuclear retaliation because several countries keep their nuclear weapons on ‘launch on warning’; in response to a warning, their leaders can decide within minutes whether they want to launch a retaliatory strike.

For the balance of terror to be a balance, all parties need to be in control at all times. This however is not the case.

In the timeline, you can read through some of the close calls during the past decades.

The risk of nuclear war might well be low – because neither side would want to fight such a war that would have such awful consequences for everyone on the planet. But there is a risk that the kinds of technical errors and accidents listed here could lead accidentally to the use of nuclear weapons, as a nuclear power can incorrectly come to believe that they are under attack.

This is why false alarms, errors, and close calls are so crucial to monitor: they are the incidents that can push the ‘balance of terror’ out of balance and into war.

Accidents and errors are of course not the only possible path that could lead to the use of nuclear weapons. There is the risk of a terribly irresponsible person leading a country possessing nuclear weapons. There is the risk of nuclear terrorism, possibly after a terrorist organization steals weapons. There is the possibility that hackers can take control of the nuclear chain of command. And there is the possibility that several of these factors play a role at the same time.

A timeline of nuclear weapons ‘close calls’ 7

Below this post, you find additional lists of close calls, where you find much more information on each of these incidents.

How to reduce the risk of nuclear war?

An escalating conflict between nuclear powers – but also an accident, a hacker, a terrorist, or an irresponsible leader – could lead to the detonation of nuclear weapons.

Those risks only go to zero if all nuclear weapons are removed from the world. I believe this is what humanity should work towards, but it is exceedingly hard to achieve, at least in the short term. It is therefore important to see that there are additional ways that can reduce the chance of the world suffering the horrors of nuclear war. 8

A more peaceful world : Many world regions in which our ancestors fought merciless wars over countless generations are extraordinarily peaceful in our times. The rise of democracy, international trade, diplomacy, and a cultural attitude shift against the glorification of war are some of the drivers credited for this development. 9

Making the world a more peaceful place will reduce the risk of nuclear confrontation. Efforts that reduce the chance of any war reduce the chance of nuclear war.

Nuclear treaties : Several non-proliferation treaties have been key in achieving the large reduction of nuclear stockpiles. However, key treaties – like the Intermediate-Range Nuclear Forces (INF) Treaty between the US and Russia – have been suspended and additional agreements could be reached.

The UN Treaty on the Prohibition of Nuclear Weapons, which became effective in 2021, is a recent development in this direction.

Smaller nuclear stockpiles : Reducing the stockpiles further is seen as an important and achievable goal by experts.

It is considered achievable because smaller stockpiles would still provide the deterrence benefits from nuclear weapons. And it is important as it reduces the risk of accidents and the chance that a possible nuclear war would end civilization.

Better monitoring, better control: The risk can be further reduced by efforts to better control nuclear weapons – so that close calls occur less frequently. Similarly better monitoring systems would reduce the chance of false alarms.

Taking nuclear weapons off ‘hair-trigger alert’ would reduce the risk that any accident that does occur can rapidly spiral out of control. And a well-resourced International Atomic Energy Agency can verify that the agreements in the treaties are met.

Better public understanding, global relations, and culture : Finally I also believe that it will help to see clearly that billions of us share the same goal. None of us wants to live through a nuclear war, none of us wants to die in one. As Reagan said, a nuclear war cannot be won and it would be better to do away with these weapons entirely.

A generation ago a broad and highly visible societal movement pursued the goal of nuclear disarmament. These efforts were to a good extent successful. But since then, this goal has unfortunately lost much of the attention it once received – and this is despite the fact that things have not fundamentally changed: the world still possesses weapons that could kill billions. 10 I wish it was a more prominent concern in our generation so that more young people would set themselves the goal to make the world safe from nuclear weapons.

Below this post you find resources on where you can get engaged or donate, to help reduce the danger from nuclear weapons.

I believe some dangers are exaggerated – for example, I believe that the fear of terrorist attacks is often wildly out of proportion with the actual risk. But when it comes to nuclear weapons I believe the opposite is true.

There are many today who hardly give nuclear conflict a thought and I think this is a big mistake.

For eight decades, people have been producing nuclear weapons. Several countries have dedicated vast sums of money to their construction. And now we live in a world in which these weapons endanger our entire civilization and our future.

These destructive weapons are perhaps the clearest example that technology and innovation are not only forces for good, they can also enable catastrophic destruction.

Without the Second World War and the Cold War, the world might have never developed these weapons and we might find the idea that anyone could possibly build such weapons unimaginable. But this is not the world we live in. We live in a world with weapons of enormous destructiveness and we have to see the risks that they pose to all of us and find ways to reduce them.

I hope that there are many in the world today who take on the challenge to make the world more peaceful and to reduce the risk from nuclear weapons. The goal has to be that humanity never ends up using this most destructive technology that we ever developed.

Resources to continue reading and finding ways to reduce the risk of nuclear weapons

• Hiroshima : John Hersey’s report for the New Yorker about the bombing of Hiroshima, published in August 1946.
• ’80,000 Hours’ profile on Nuclear Security : an article focusing on the question of how to choose a career that makes the world safer from nuclear weapons.
• The ‘Future of Life Institute’ on Nuclear Weapons : this page includes an extensive list of additional references – including videos, research papers, and many organizations that are dedicated to reducing the risk from nuclear weapons.

Acknowledgments: I would like to thank Charlie Giattino, Hannah Ritchie, and Edouard Mathieu for reading drafts of this and for their very helpful comments and ideas.

Additional lists of close calls with nuclear weapons

* Future of Life Institute – Accidental nuclear war: A timeline of close calls .

* Alan F. Philips, M.D. – 20 Mishaps That Might Have Started Accidental Nuclear War , published on Nuclear Files

* Josh Harkinson (2014) – That Time We Almost Nuked North Carolina

* Union of Concerned Scientists (2015) – Close Calls with Nuclear Weapons

* Chatham House Report (2014) – Too Close for Comfort: Cases of Near Nuclear Use and Options for Policy authored by Patricia Lewis, Heather Williams, Benoît Pelopidas, and Sasan Aghlani

* Wikipedia – List of Nuclear Close Calls

On Nuclear Winter see:

* Jägermeyr, Jonas, Alan Robock, Joshua Elliott, Christoph Müller, Lili Xia, Nikolay Khabarov, Christian Folberth, et al. (2020) – ‘ A Regional Nuclear Conflict Would Compromise Global Food Security’ . Proceedings of the National Academy of Sciences 117, no. 13 (31 March 2020): 7071–81.

* Robock, A., L. Oman, and G. L. Stenchikov (2007) – Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences , J. Geophys. Res., 112, D13107, doi:10.1029/2006JD008235.

* Alan Robock & Owen Brian Toon (2012) – Self-assured destruction: The climate impacts of nuclear war . In Bulletin of the Atomic Scientists, 68, 66–74.

* Alan Robock & Owen Brian Toon (2016) – Let’s End the Peril of a Nuclear Winter , In the New York Times, Feb. 11, 2016.

Some additional points:

* The risk of nuclear winter (initially termed ‘nuclear twilight’) was only discovered in the early 1980s, more than 3 decades after the bombs were first used.

* The main mechanism by which a nuclear winter is expected to cause a decline in global food production is by reducing the growing season, the days in a row without frost. See Robock, Oman, and Stenchikov (2007).

* Robock estimates that the smoke and soot would rise as high as 40 kilometers (25 miles) into the atmosphere. See Robock and Toon (2016).

* Before the nuclear famine kills people from hunger, many will die from hypothermia.

* In addition to the impact on the climate, the ozone layer is expected to get depleted in such a scenario. This would allow more ultraviolet radiation to reach our planet’s surface, harming plant and animal life.

* In general there is only relatively little scientific work that focuses on nuclear winter and additional, good research could be useful to provide a better understanding. Due to the lack of research there remains uncertainty about how devastating a nuclear winter would be. In particular there is disagreement on how likely it is that all of humanity would die in a nuclear winter.

* The paper by Jägermeyr et al (2020) shows that among the countries with the largest food production losses would be the US and Russia, those countries that have the largest stockpiles of nuclear weapons.

For anyone who interested in the impact of nuclear winter on food production and famine, Ord (2020) cites the following:

* Cropper, W. P., and Harwell, M. A. (1986) – “Food Availability after Nuclear War,” in M. A. Harwell and T. C. Hutchinson (eds.), The Environmental Consequences of Nuclear War (SCOPE 28), vol. 2: Ecological, Agricultural, and Human Effects. John Wiley and Sons.

* Helfand, I. (2013) – Nuclear Famine: Two Billion People at Risk? Physicians for Social Responsibility.

* Xia, L., Robock, A., Mills, M., Stenke, A., and Helfand, I. (2015) – Decadal Reduction of Chinese Agriculture after a Regional Nuclear War . Earth’s Future, 3(2), 37–48.

Reagan in his State of the Union address in 1984, quoted in the New York Times: Bernard Gwertzman (1984) – Reagan reassures Russians on war . In the New York Times January 26, 1984.

There are nine countries that are known to possess nuclear weapons: Russia, United States, France, China, United Kingdom, Israel, Pakistan, India, and North Korea. South Africa once possessed nuclear weapons and is the first state to voluntarily give up nuclear weapons.

The explosive power of a nuclear weapon is called the yield of a nuclear weapon. It is the amount of energy released when that weapon is detonated. It is usually measured in ‘TNT equivalents’.

The bomb that the US dropped on Hiroshima had a yield of 13–18 kilotons of TNT. (one kiloton are 1000 tonnes)

The largest bomb that was ever detonated is the ‘Tsar Bomba’ built by the USSR and detonated in October 1961. Its yield was about 50 megatons of TNT. That’s 50,000 kilotons of TNT or about 3,333-times the yield of the bomb in Hiroshima.

The scenario in Robock, Oman, and Stenchikov (2007) is based on the nuclear stockpiles after the large reduction that was achieved after the end of the Cold War. It shows that the world still retains enough weapons to produce “a large, long-lasting, unprecedented global climate change,” as the authors put it. Since the publication of this study, the stockpiles have been reduced further, as the chart shows, but not very strongly so.

For a recent discussion of this question see Ord (2020) – The Precipice.

This list is largely based on Toby Ord’s 2020 book The Precipice . His list can be found in Chapter 4 and Appendix C of his book.

Ord in turn relies mostly on a document from the US Department of Defense from 1981: Narrative Summaries of Accidents Involving US Nuclear Weapons (1950–1980) .

This list is mostly based on the ’80,000 Hours’ profile on Nuclear Security and Toby Ord (2020) – The Precipice.

For big overviews of this literature see the forthcoming book Christopher Blattman (2022) – Why We Fight: The Roots of War and the Paths to Peace and Steven Pinker (2011) – The Better Angels of our Nature for a big overview

Lawrence S. Wittner – Confronting the Bomb: A Short History of the World Nuclear Disarmament Movement . Stanford University Press.

One indication for the declining interest in the last generation: Mentions of “nuclear war” in books and newspapers peaked in 1985 and declined strongly since then (see Google Ngram for ‘nuclear war’ ).

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• Added North Korea to the list of declared nuclear states.
• Updated U.S. nuclear arsenal page.
• Updated Operation Castle test page and Nuclear Weapons Frequently Asked Questions, Section 12 . Contact email changed.
• Site is retitled The Nuclear Weapon Archive with its own domain.
• 14.0 Nuclear Weapons FAQ Change History Major Reference Articles and Links Repository of Nuclear Effects Computer Simulations and Models Illustrated Effects of Nuclear Weapons Plutonium Manufacture and Fabrication (illustrated) The Smyth Report: Atomic Energy for Military Purposes; the first public description of atomic technology, released in 1945 and still an excellent introduction Nuclear Tests Comprehensive List of All Nuclear Explosions by Jim Lawson [8/1996] Official List of Underground Nuclear Explosions in Nevada [1995] Bibliographic Material Some References [1995] The Big List of Nuclear Weapons Publications [1995] Links to Important Information Sites. Maintaining links to web resources is a challenge. The links listed here all work as of the beginning of 2020. The Department of Energy home page is an excellent place to start. Several pages of excellent links to other DOE information sites are accessible from here. U.S. Department of Energy Office of Scientific and Technical Information . Excellent link for accessing millions of pages of on-line information. Lawrence Livermore National Laboratory has shut down its library search portal and LLNL reports can be found here. Government Accounting Office Report Page . A valuable resource. Go to GAO Access Search Page, use keyword search (like "nuclear"). Many FY 95 and later reports are available online Complete Archive Site for the late lamented U.S. Office of Technolgy Assessment (OTA) . Hosted by Princeton Univ. Federation of American Scientists: Nuclear resources Lots of stuff here, browse around. Stephen Schwartz's list of U.S. Nuclear Weapons Facilities Brookings Institute Nuclear Weapons Cost Study Home Page Gregory Walker's Trinity Site The Bulletin of the Atomic Scientists , this site now hosts the text of many valuable articles, with on-line search capability. Natural Resources Defense Council (NRDC) James Martin Center for Nonproliferation Studies (CNS) at the Monterey Institute of International Studies (MIIS). Excellent repository of on-line materials British American Security Information Council (BASIC) . An independent research organization that analyzes government policies. Project On Government Oversight (POGO): Center for Defense Information (CDI) An independent military policy research and analysis organization, has many on-line resources. Medical Management of Radiological Casualties Good resource on biological and chemical weapons. FM 8-9: Nato Handbook on the Medical Aspects of NBC Defensive Operations
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Nuclear Weapons, Peace and the Security Dilemma: The Role of Cognitive Processes in Deterrence

For the past forty years, deterrence theory has played a central role in the evolution of U.S. nuclear strategy and national security policy. Proponents of deterrence point to the historical record to argue the theory “works”. Recent critiques of the theory have emphasized, however, that many of the fundamental questions regarding how deterrence works remain unanswered. For example, how do decision makers decide “how much is enough” to deter aggression? What role do cognitive processes play in deterrent decisions? The research described in this paper was designed to examine such questions. Specifically, the effects of decision frame, salience of intergroup boundaries, and feedback regarding the economic consequences of decisions on deterrent behavior were investigated using a laboratory analogue of a security dilemma. Results from two experiments are presented. The first experiment confirms that decision frame and categorization can adversely affect deterrent allocations. The second experiment suggests that reframing decisions and providing feedback regarding the costs of deterrence might reduce decision makers’ tendency to over-allocate resources for defense. The external validity of these findings are discussed, as well as implications of such research for the study of peace among the nuclear powers.

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Numbers, Facts and Trends Shaping Your World

Read our research on:

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Nuclear Weapons

Iran widely criticized in 14 advanced economies.

A median of about seven-in-ten people in 14 countries expressed unfavorable views of Iran, while only about two-in-ten hold a favorable view.

Foreign policy experts in the U.S. have much different views about threats to the country than the general public

International relations experts’ assessment of the current crises facing the world are often at odds with those of the U.S. general public.

Americans See Spread of Disease as Top International Threat, Along With Terrorism, Nuclear Weapons, Cyberattacks

Most say cooperation with other countries is important in dealing with global threats, especially on the spread of infectious diseases.

Before Soleimani’s death, concerns about Iran had fallen in many countries – including the U.S.

Asked in spring 2019 which country or group poses the greatest threat to their country in the future, just 6% of Americans named Iran.

Global concerns persist about North Korea’s nuclear program before second Trump-Kim summit

A median of 52% across 26 countries consider North Korea’s nuclear program to be a major threat to their country.

5 facts about how the U.S. and its allies see North Korea

Eyes turn to Singapore this week as President Donald Trump and North Korean leader Kim Jong Un prepare to meet for the first time. While previous communication between the two leaders was marked by hostility, the meeting came about following North Korea’s more recent promises to suspend missile tests and discuss denuclearization. Here are five […]

Public Is Skeptical of the Iran Agreement – and Trump’s Handling of the Issue

As Donald Trump prepares to announce his long-awaited decision on the Iran nuclear agreement, more Americans say they disapprove (40%) than approve (32%) of the agreement.

Increasing Public Concern Over North Korea’s Nuclear Capability, Intentions

As Donald Trump sets off on his visit to Asia, the public has become increasingly concerned over North Korea’s capability and its willingness to use nuclear weapons against the United States.   

In Asia-Pacific countries, many are concerned about North Korea’s nuclear program

Americans and many in the Asia-Pacific region hold negative views of North Korea and its nuclear weapons program but are divided on what to do about it.

Americans hold very negative views of North Korea amid nuclear tensions

Overall, 78% of Americans have an unfavorable view of the communist nation ruled by Kim Jong Un, with 61% holding a very unfavorable opinion.

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What Public Opinion Says About the Use of Nuclear Weapons

There is a hard-fought and critical debate about whether or not there is a norm against the use of nuclear weapons. A nuclear war could lead to the end of life as we know it on a global scale. If humans believe that nuclear weapons should not be used, then we can have some confidence that humans are unlikely to use them. If, however, there is not a norm against their use, we cannot be confident that the U.S. nuclear bombing of Hiroshima and Nagasaki in Japan will remain the world’s only case of a nuclear attack.

With the return of great power rivalry, the Russo-Ukrainian war, and President Vladimir Putin’s and former President Donald Trump’s threats of nuclear use, the matter of nuclear norms is highly salient. Norms identify standards of appropriate behavior. In the case of nuclear weapons, we might think of there being a tradition against their use. A taboo against nuclear use is even stronger than a norm; it is an unconditional proscription. Violators of a taboo are seen as morally loathsome.

The study of nuclear norms often includes examination of the views of policymakers or individuals as a group. Depending on what questions a survey asks and how the questions are phrased, the research might find that the public is strongly against the use of nuclear weapons. The U.S. public is widely assumed to believe that nuclear weapons use is bad. But new research by Joshua Schwartz, an assistant professor at the Carnegie Mellon Institute for Strategy & Technology, finds high support for their use, even when foreign countries press the nuclear “button.”

Could you tell us briefly why your article matters?

My article analyzes the extent to which public opinion might constrain leaders from using — or enable leaders to use — nuclear weapons. Like global pandemics, nuclear weapons use is a high-impact but low-probability event. It is low probability in the sense that states have strong incentives not to use nuclear weapons, which can help explain why they (thankfully) have not been used for almost 80 years. It is high impact in the sense that the use of even a single modern nuclear weapon could cause unthinkable devastation.

Worryingly, there are signs the risk of nuclear use has increased in recent years. Vladimir Putin has issued nuclear threats in the context of the Russo-Ukraine War. As president, Donald Trump publicly warned North Korea of possible U.S. nuclear use (the infamous “fire and fury” threat) and privately discussed the use of nuclear weapons with his advisors. China is engaged in a large-scale nuclear buildup that will see its arsenal double by 2030. Cold War-era nuclear arms control agreements between the United States and Russia, such as the New START and Intermediate-Range Nuclear Forces Treaties, have collapsed or are near collapse. Consequently, how the public views the use of nuclear weapons is an important question.

What is the conventional wisdom on public opinion about nuclear weapons?

The conventional wisdom is that foreign audiences in particular would condemn the use of nuclear weapons by the United States. For example, Secretary of State John Foster Dulles argued that using nuclear weapons in response to a Soviet blockade on Berlin in 1948 “would surely cost us our allies” and “we’d be finished as far as present-day world opinion was concerned.” Regarding the possibility of using nuclear weapons in Vietnam, President Richard Nixon said that doing so would have resulted in “domestic and international uproar [that] would have damaged our foreign policy on all fronts.” General Matthew Ridgway, who became Supreme Allied Commander in Europe and the U.S. Army chief of staff, argued that using nuclear weapons “would so revolt free world opinion as to leave us, quite possibly, friendless and isolated in a hostile world.”

Related Article

In general, many scholars argue that there is a strong norm, tradition , or even taboo against the use of nuclear weapons. Because of the unique scale and speed at which nuclear weapons can inflict destruction, policymakers and the public may view their use as fundamentally inappropriate. The best evidence for this position is that nuclear weapons have not been used since 1945, even against countries that could not threaten nuclear retaliation themselves. If nuclear deterrence does not explain historical non-use, then perhaps a norm against nuclear use can.

How does your research differ from previous studies on public opinion about nuclear weapons?

Scholars have asked whether the public would support the use of nuclear weapons by their own government. Surveys conducted in the United States , China , and other major powers indicate that a majority or near-majority of the public would support the use of nuclear weapons by their own country if doing so would enhance military effectiveness or save the lives of co-national soldiers. My article takes a different approach. I ask whether the public would support the use of nuclear weapons by a foreign government.

What are your main findings?

Surprisingly, my research finds high support for hypothetical nuclear use, even when foreign countries press the nuclear “button.” In four survey experiments involving members of the public in the United States and India, support for hypothetical nuclear use is the same when an individual’s own country hypothetically uses nuclear weapons as when a foreign allied or partner country hypothetically uses nuclear weapons. For example, in one study on the U.S. public, support for a hypothetical nuclear attack against Iran was no different when Israel carried it out compared to the United States. Overall, I found that the use of nuclear weapons is not taboo in the United States and India. But support is lower when the public considers a non-allied or non-partner country’s hypothetical use of nuclear weapons.

The use of violence by in-group members is likely to be seen as more ethical and receive greater levels of support than the use of violence by out-group members.

The key to understanding these findings is the concept of in-groups and out-groups. In-group bias means that individuals are more likely to favor members of their own group (“us”) than members of other groups (“them”). In-groups are based on an understanding of a shared attribute. National identification is one of the most powerful shared attributes making up an individual’s identity. Other shared attributes — such as values, ideologies, and interests — can also shape perceptions of us versus them. Individuals may view allied and partner countries as part of their in-group because they share values, ideologies, and interests with an individual’s own country. For example, U.S. citizens may consider formally allied countries (e.g., NATO members like France) and more informal partners (e.g., Israel, which does not have a formal defense agreement with the United States) as part of their in-group.

Per “ virtuous violence theory ” (VVT) in psychology, the use of violence by in-group members is likely to be seen as more ethical and receive greater levels of support than the use of violence by out-group members because humans value unity within their in-group. All of this suggests that when in-group countries use nuclear weapons, support may be higher than the conventional wisdom suggests.

Can you say more about VVT?

VVT maintains that people typically engage in or support violence because they believe that it is moral — or “virtuous” — to do so. In other words, people view it as the right thing to do even if they do not inherently enjoy committing or observing violence. People believe that resorting to violence is sometimes the right thing to do because the use of or support for violence can help create, maintain, or enhance social relationships. For example, most would agree that using violence to protect your own child against the threat of an armed home invader is moral.

According to the VVT framework, an in-group member’s use of violence to protect the larger group against a threat is likely to be perceived as a virtuous action that reinforces collective responsibility and outcomes. In contrast, an out-group member’s use of violence will be viewed as less virtuous because the moral imperative of unity will not be at play. This difference reflects in-group bias.

Tell us more about how you conducted your research and what you found.

In the surveys, I presented respondents with hypothetical scenarios in which a country might consider using nuclear weapons (e.g., in a war with Iran or against a terrorist group with a deeply buried nuclear weapons lab). I then randomly varied the country hypothetically using nuclear weapons in the surveys. For the studies on the U.S. public, the possibilities included the United States (an individual’s own country), France (a treaty ally), Israel (a close partner), Pakistan (a “frenemy”), and Russia (a current adversary and clear out-group country). Besides the country carrying out the hypothetical nuclear strike, all the other details of the scenario were the same.

The results were striking. Contrary to the conventional wisdom, U.S. public support did not drop when France or Israel carried out a hypothetical nuclear attack compared to when the United States did so. Absolute levels of support for nuclear use were also high, with a majority or near-majority approving of a hypothetical nuclear attack by the United States, France, or Israel. The findings related to the scenario about Iran were particularly sobering, as that hypothetical involved intentionally attacking 100,000 Iranian civilians with nuclear weapons.

Although U.S. public support was lower for a hypothetical Pakistani or Russian nuclear strike than for a hypothetical U.S. strike, about two-fifths of respondents still supported it.

Essentially identical results held among the Indian public. Support for a nuclear strike by the United States (a strategic partner of India’s) was not lower than support for a nuclear attack by the Indian government. On the other hand, support was significantly less for a nuclear strike by Pakistan (a clear enemy of India’s). Absolute levels of support were again high, with a majority supporting a nuclear strike by India and the United States, and over one-third of respondents supporting a nuclear attack by Pakistan.

Overall, nuclear use seems far from unthinkable for many members of U.S. and Indian publics, even when foreign countries are the attackers. Public opinion opposing nuclear use may thus be less restrictive for policymakers than previously thought.

Jacqueline L. Hazelton is the executive editor of the journal International Security.

Joshua A. Schwartz is an assistant professor at the Carnegie Mellon Institute for Strategy & Technology (CMIST). His article “ When Foreign Countries Push The Button: Public Support for Foreign Nuclear Use ” appears in the Spring 2024 issue of International Security.

83 Nuclear Weapon Essay Topic Ideas & Examples

🏆 best nuclear weapon topic ideas & essay examples, 📌 simple & easy nuclear weapon essay titles, 👍 good essay topics on nuclear weapon, ❓ research questions about nuclear weapons.

• Means of Destruction & Atomic Bomb Use Politics This information relates to the slide concerning atomic energy, which also advocates for the participation of the Manhattan Project’s researchers and policy-makers in the decision to atomic bombing during World War II.
• Can a Nuclear Reactor Explode Like an Atomic Bomb? The fact is that a nuclear reactor is not designed in the same way as an atomic bomb, as such, despite the abundance of material that could cause a nuclear explosion, the means by which […]
• Ethics and Sustainability. Iran’s Nuclear Weapon The opponents of Iran’s nuclear program explain that the country’s nuclear power is a threat for the peace in the world especially with regards to the fact that Iran is a Muslim country, and its […]
• The Decision to Drop the Atom Bomb President Truman’s decision to use the atomic bomb on the Japanese cities of Hiroshima and Nagasaki was a decision of unprecedented complexity and gravity and, without a doubt, the most difficult decision of his life.
• E. B. Sledge’s Views on Dropping the A-Bomb There is a pointed effort to present to the reader the reality of war in all its starkness and raw horror. However, in the case of a war veteran like E.B.
• The Atomic Bomb of Hiroshima The effects of the bombing were devastating; the explosion had a blast equivalent to approximately 13 kilotons of TNT. Sasaki says that hospitals were teaming with the wounded people, those who managed to survive the […]
• Was the US Justified in Dropping the Atomic Bomb? In addition to unleashing catastrophic damage upon the people of Japan, the dropping of the bombs was the beginning of the Cold War between the Soviet Union and the U.S.
• Middle East: Begin Doctrine and Nuclear Weapon Free Zone This happens to be the case despite the fact that many countries and different members of the UN have always been opposed to the validity and applicability of this foreign doctrine or policy.
• Atomic Bomb as a Necessary Evil to End WWII Maddox argued that by releasing the deadly power of the A-bomb on Japanese soil, the Japanese people, and their leaders could visualize the utter senselessness of the war.
• Nuclear Weapon Associated Dangers and Solutions The launch of a nuclear weapon will not only destroy the infrastructure but also lead to severe casualties that will be greater than those during the Hiroshima and Nagasaki attacks.
• Why the US Decided to Drop the Atomic Bomb on Japan? One of the most notable stains on America’s reputation, as the ‘beacon of democracy,’ has to do with the fact that the US is the only country in the world that had used the Atomic […]
• The Marshallese and Nuclear Weapon Testing The other effects that the Marshallese people suffered as a result of nuclear weapon testing had to do with the high levels of radiations that were released.
• Was the American Use of the Atomic Bomb Against Japan in 1945 the Final Act of WW2 or the Signal That the Cold War Was About to Begin Therefore, to evaluate the reasons that guided the American government in their successful attempt at mass genocide of the residents of Hiroshima and Nagasaki, one must consider not only the political implications behind the actions […]
• Leo Szilard’s Petition on the Atomic Bomb The group of scientists who created the weapon of mass destruction tried to prevent the usage of atomic bombs with the help of providing the petition to the President.
• Atomic Audit: Nuclear Posture Review Michael notes that the use of Weapons of Mass Destruction, such as nuclear bombs, tends to qualify the infiltration of security threats in the United States and across the world.
• Why the US used the atomic bomb against Japan? There are two main reasons that prompted the United States to use the atomic bomb against Japan; the refusal to surrender by Japan and the need for the US to assert itself.
• The Use of Atomic Bomb in Japan: Causes and Consequences The reason why the United States was compelled to employ the use of a more lethal weapon in Hiroshima and Nagasaki in Japan has been at the heart of many scholarly writings.
• The Tradition of Non Use of Nuclear Weapon It is worth noting that since 1945 the concept of non use of nuclear weapons have occupied the minds of scholars, the general public and have remain the most and single important issues in the […]
• Was it Necessary for the US to Drop the Atomic Bomb? When it comes to discussing whether it was necessary to drop atomic bombs on Japan’s cities of Hiroshima and Nagasaki in August of 1945, it is important to take into account the specifics of geopolitical […]
• Iran and Nuclear Weapon However, whether world leaders take action or not, Iran is about to get the nukes, and the first target will be Israel followed by American and the rest of the world.
• An Analysis of the United States’ Nuclear Weapon and the Natural Resources Used to Maintain it
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Biden Approved Secret Nuclear Strategy Refocusing on Chinese Threat

In a classified document approved in March, the president ordered U.S. forces to prepare for possible coordinated nuclear confrontations with Russia, China and North Korea.

By David E. Sanger

David E. Sanger has written about American nuclear strategy for The New York Times for nearly four decades.

President Biden approved in March a highly classified nuclear strategic plan for the United States that, for the first time, reorients America’s deterrent strategy to focus on China’s rapid expansion in its nuclear arsenal.

The shift comes as the Pentagon believes China’s stockpiles will rival the size and diversity of the United States’ and Russia’s over the next decade.

The White House never announced that Mr. Biden had approved the revised strategy, called the “Nuclear Employment Guidance,” which also newly seeks to prepare the United States for possible coordinated nuclear challenges from China, Russia and North Korea. The document, updated every four years or so, is so highly classified that there are no electronic copies, only a small number of hard copies distributed to a few national security officials and Pentagon commanders.

But in recent speeches, two senior administration officials were allowed to allude to the change — in carefully constrained, single sentences — ahead of a more detailed, unclassified notification to Congress expected before Mr. Biden leaves office.

“The president recently issued updated nuclear-weapons employment guidance to account for multiple nuclear-armed adversaries,” Vipin Narang, an M.I.T. nuclear strategist who served in the Pentagon, said earlier this month before returning to academia. “And in particular,” he added, the weapons guidance accounted for “the significant increase in the size and diversity” of China’s nuclear arsenal.

In June, the National Security Council’s senior director for arms control and nonproliferation, Pranay Vaddi, also referred to the document , the first to examine in detail whether the United States is prepared to respond to nuclear crises that break out simultaneously or sequentially, with a combination of nuclear and nonnuclear weapons.

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Nuclear Testing

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JOE BARONIO, REPORTER: On July 16th, 1945, this explosion in the desert of New Mexico changed the world forever. It was a test of the world's first nuclear bomb called Trinity, and it was the turning point for one of the most dangerous races in human history.

The nuclear story actually begins a few years earlier in 1938, when three German scientists discovered something called Nuclear Fission, which is when atoms are split in a chain reaction and release a huge amount of energy. And when World War II began in 1939, a race began to use this new discovery to build a super-bomb.

This famous physicist, Albert Einstein, actually wrote to the US president urging him to do it because he was worried the NAZIs would figure it out first and, in a top-secret project led by this guy, J. Robert Oppenheimer, the Americans developed and tested the world's first nuclear weapon.

Two weeks later, in August 1945, they dropped two bombs on Hiroshima and Nagasaki.

MAN: The bomb is dropped.

The cities were almost entirely destroyed and hundreds of thousands of people died. While Japan surrendered, many were horrified including the man who built the bomb.

J. ROBERT OPPENHEIMER: Now I am become death, the destroyer of worlds.

The threat of nuclear weapons didn't end with the war.

PUBLIC AWARENESS CAMPAIGN: Please duck and cover.

This is an actual video shown to kids in the US back in the 50s when many people were worried about a nuclear attack. America had a new enemy, the Soviet Union. They were developing and testing their own nuclear weapons, and the U.S. and its allies were racing to keep up, conducting tests in locations around the world. At the time, many people didn't realise that just testing these weapons could have catastrophic impacts. See, each blast creates massive amounts of tiny radioactive particles called fallout which can poison people and the environment. That happened to Bikini Atoll in the Marshall Islands when, on the first of March 1954 the U.S. set off its largest nuclear detonation ever: Castle Bravo.

BIKINI ATOLL RESIDENT: The earth shook. Most of us were very afraid.

JOE BARONIO: Lots of Marshallese people suffered radiation sickness and died, and the islands are still contaminated. In Australia, the United Kingdom detonated twelve bombs in The Montebello Islands, Emu Field, and Maralinga.

MARALINGA RESIDENT: We all got sick. Diarrhea, vomiting, and sore eyes, I couldn't open my eyes.

JOE BARONIO: But the testing continued. In 1961, the Soviets dropped Tsar Bomba, the most powerful weapon the world has ever seen over the Arctic Ocean. France, China and India also tested nuclear weapons until the 1990s, but as time went on more and more people spoke out against them.

KID: We just want our world to live because it's a nice place.

JOE BARONIO: In 1995 there were huge protests over French tests in the Pacific, and the following year many countries signed an agreement to ban nuclear weapons tests completely. These days, nuclear tests are basically unheard of, and the number of nuclear weapons is continuing to drop. And since 2009 the UN has marked August 29 as the International Day Against Nuclear Testing to remind us all of the devastating power of these super-weapons.

August 29th is the International Day against Nuclear testing. It’s something we don’t see today but not too long-ago nuclear tests were being carried out around the world. We find out more about the history of nuclear testing and its legacy on people and the planet.

• Joseph Baronio, Reporter

BTN Classroom Episode 24, 2024

5 items In this episode

Paralympic history.

Arisa Trew Interview

Water on Mars

Rose's Drama Class

Nuclear Tests

Maralinga History

BTN: Nuclear tests at Maralinga

Ending Nuclear Testing – United Nations

Nuclear bombs vaporised parts of the bikini atoll decades ago. what are the lasting impacts today.