Abstract. significant policy implications as mature nuclear powers currently face decisions about

Transcription

1 Abstract This study builds on a growing body of recent scholarship of nuclear security and evaluates states decisions about delivery platforms after acquiring nuclear weapons. Enhancing understanding of nuclear force structure decisions and underlying motives has significant policy implications as mature nuclear powers currently face decisions about modernizing their arsenals and nascent nuclear powers choose which types of platforms to develop. This study anticipates that states diversification of platforms will reflect economic constraints and varied thinking about the utility of nuclear weapons. Three main hypotheses to explain nuclear force structure decisions are proposed including affordability, survivability, and usability. Quantitative findings for both the affordability and survivability hypotheses are inconclusive. Stronger evidence is found for the usability hypothesis supporting the view that states deploy a greater number of tactical platforms in response to growing conventional threats. This quantitative evidence is paired with qualitative case studies exploring the dynamics of force structure decisions in both Pakistan and the United States that reflect the expectations of the usability and survivability hypotheses. 1

2 Acknowledgments The continuing guidance and support of my advisors Dr. Stephen Gent, Dr. Patricia Sullivan, and Dr. Kyle Beardsley made this paper possible. Their suggestions and commentary helped expand and sharpen my own thinking throughout this project from beginning to end. I am also deeply indebted to Dr. Joseph Caddell for inspiring my interest in nuclear security issues, as well as his thoughtful suggestions for my research and frequent encouragement. I am grateful for the efforts of Erik Gartzke, Jeffrey Kaplow, and Rupal Mehta in compiling a dataset on nuclear portfolio diversification that provided a crucial foundation in constructing the dataset for this study. My Peace, War, and Defense family and especially Jackie Gorman were also incredibly supportive throughout this project and druing my whole time at Carolina. I sincerely appreciate the perceptive insights and comments of friends who listened to my musings on this topic and provided feedback on earlier drafts, especially Corie Walsh, Brendan Cooley and Becca Arbacher. Finally, I would like to thank my family for always pushing me to challenge myself and for their unfailing love and support. 2

3 Table of Contents List of Tables List of Abbreviations 4 4 Chapter 1: Introduction 5 Context and Research Question 5 Quantitative vs. Qualitative Approaches 10 Policy Significance 14 Chapter 2: Literature Review 16 The Nuclear Renaissance 16 Catalogues of Delivery Platforms 17 State Specific Studies of Nuclear Force Structures 18 Quantitative Studies 20 Nuclear Strategic Schools of Thought 23 Chapter 3: Theoretical Expectations 27 Motivations for Diversification 27 Affordability, Survivability, and Usability 29 Chapter 4: Research Design and Quantitative Findings 32 Dependent Variables 33 Explanatory Variables 35 Modeling Approach 37 Findings 37 Chapter 5: Qualitative Findings and Case Studies 43 Challenges of Affordability Hypothesis 43 Survivability Case Study: United States 44 Seeking Survivability 46 Alternative Explanations for Diversification 49 Limitations of the Survivability Hypothesis 52 Usability Case Study: Pakistan 53 Origins of Pakistan s Nuclear Program 54 Shifts in Force Posture 59 Alternative Explanations for Diversification Qualifications of Usability Hypothesis Conclusion Chapter 6: Conclusion 65 Policy Significance 65 Discussion of Methods and Findings 66 Further Research Bibliography Data Appendix

4 List of Tables Table 1: Descriptive Statistics Table 2: Affordability Hypothesis Table 3: Survivability Hypothesis Table 4: Usability Hypothesis List of Abbreviations ABM Antiballistic Missile GDP Gross Domestic Product ICBM Intercontinental Ballistic Missile IRBM Intermediate Range Ballistic Missile MAD Mutually Assured Destruction MID Militarized Interstate Dispute MIRV Multiple Independently Targeted Reentry Vehicles SLBM Submarine Launched Ballistic Missile SSBN Ship, Submersible, Ballistic, Nuclear TNW Tactical Nuclear Weapons USAF United States Air Force USN United States Navy 4

5 Chapter 1: Introduction Context and Research Question Over seventy years after the dawn of the atomic age, nuclear weapons remain an imperative issue in the realm of international security. Nuclear proliferation and strategy continue to pose challenging policy questions throughout the international system. From concerns about horizontal proliferation and the behavior of nascent nuclear powers to discussions about the modernization of the arsenals of Russia and the United States, nuclear weapons continue to draw considerable attention. The persistent nuclear rivalry between the United States and Soviet Union during the Cold War and recurring concerns over proliferation have generated substantial scholarly research on nuclear security. The bulk of existing research has attempted to explain states nuclear ambitions, as well as the effect of these weapons on international security. 1 Recent, scholarship has begun to explore nuclear decision-making in greater detail and also employ quantitative analyses to key nuclear issues. 2 After states acquire an initial nuclear capability they must decide what delivery platforms they already possess, are able to acquire, or can successfully develop and deploy. This study seeks to answer the question of why states choose to deploy the 1 For examples on states nuclear ambitions see: Scott D. Sagan, Why Do States Build Nuclear Weapons?: Three Models in Search of a Bomb, International Security 21, no. 3 (1996): 54 86; Joseph Cirincione, Bomb Scare: The History and Future of Nuclear Weapons (New York: Columbia University Press, 2008); For discussion of its nuclear weapons implications for international security see: Scott Douglas Sagan and Kenneth N. Waltz, The Spread of Nuclear Weapons: An Enduring Debate, 3rd ed (New York: W.W. Norton & Co, 2013); Albert Wohlstetter, The Delicate Balance of Terror., Foreign Affairs 37, no. 1 (January 1, 1958): ; Thomas C. Schelling, The Strategy of Conflict, Second Edition (Cambridge, Mass.: Harvard Univ. Press, 1980). 2 Vipin Narang, Nuclear Strategy in the Modern Era: Regional Powers and International Conflict (Princeton University Press, 2014),

6 platforms they do. In addition to examining explanatory variables for diversification I also disaggregate the types of platforms deployed in greater detail than previous studies. States nuclear force structure, or the type of delivery vehicles they include in their arsenal, reflects strategic thinking about nuclear weapons and is closely linked to explicit or implicit doctrines outlining their use. Studies of nuclear weapons must extend beyond explaining the decision to pursue these weapons and also seek to systematically evaluate the systems they use to deploy them Broadly speaking, there are three groups of delivery vehicles: aircraft, land-based missiles, and sea-launched missiles. The most common delivery platforms are aircraft that can be fitted with either gravity bombs or air-launched missiles to deliver nuclear weapons to a target. These are the most widely available type of platform and all existing nuclear powers initially relied on aircraft as their primary delivery vehicle. The next group of systems is land-based missiles, and this has generally been the second type of system acquired by nuclear powers. Land-based missiles vary greatly in terms of range and yield, from short-range tactical missiles with smaller yields deployed on mobile launchers to much larger intercontinental ballistic missiles (ICBMs) such as the Minuteman III placed within fixed silos. Identifying differences in yield and range of land-based missiles is key to understanding the intended purpose of these platforms. The final family of platforms, and the one most difficult to develop, is sealaunched cruise and ballistic missiles deployed on submarines. As with land-based missiles these can have considerable variation in size and range as well. Given the wide variation in platforms and capabilities, understanding how states determine which systems to develop and deploy is an interesting and challenging question to consider. 6

7 Different platforms possess advantages and disadvantages and evaluating states portfolio diversification must acknowledge these differences to understand force structure decisions. Aircraft are relatively inexpensive delivery vehicles and are recallable, which gives them utility for signaling purposes. Stationary missiles have short delivery times and have simplified command and control requirements relative to mobile missiles. Mobile missiles are the most survivable but are the most costly and technologically intensive. Breaking a state s aggregate number of platforms into different subcategories allows this study to examine to what extent diversification decisions are driven by concerns about the affordability, survivability, and usability of a states arsenal. One explanation for particular force structures is strictly related to the cost of building and maintaining a state s nuclear arsenal. Nuclear arsenals must compete with other military programs for funding within constraintsed budgets. Although developing and deploying new platforms is less expensive than the total cost for acquiring initial nuclear capabilities, fielding new delivery vehicles is significant and must be considered as states decide how to structure their nuclear arsenals. Moreover, the costs for developing different delivery vehicles vary dramatically. Modifying existing aircraft to deliver a nuclear payload is significantly cheaper than indigenously developing ballistic missile platforms 3. As a consequence, when states are working with smaller military budgets they should be expected to rely more heavily on aircraft than missiles in their arsenal. The affordability hypothesis evaluates the extent to which financial constraints influence states force structure decisions. 3 Erik Gartzke, Jeffrey M. Kaplow, and Rupal N. Mehta, The Determinants of Nuclear Force Structure, Journal of Conflict Resolution 58, no. 3 (April 1, 2014): 486 7, doi: /

8 Another consideration for states as they decide how to structure their nuclear arsenals is their vulnerability to a preemptive strike by an adversary. When a state faces a nuclear rival with a growing capacity to launch an effective first-strike it can be expected to prioritize more survivable platforms and especially mobile, concealable missiles. One key advantage of concealable missiles over aircraft and stationary land-based missiles is the difficulty in targeting and destroying them. The survivability hypothesis anticipates a positive correlation between states deployment of mobile missile platforms and the growth of a rival s nuclear arsenal. One final motive for nuclear force structure decisions is the usability of a state s arsenal. If a state seeks to deter both conventional and nuclear threats with its nuclear arsenal it must be able to credibly commit to first use of nuclear weapons even in response to a conventional attack. If a state only possesses high-yield weapons or if it lacks the means for rapid dispersal and delivery it calls into question the credibility of any threat to use nuclear weapons as a response to a conventional attack. 4 An arsenal containing lower-yield and generally shorter range tactical nuclear platforms can more credibly threaten first use. As states face a growing conventional threat or if they face a conventionally superior rival they can be anticipated to deploy tactical nuclear weapons (TNWs) as a countermeasure. One of the foremost questions animating previous studies of nuclear proliferation has been why states seek to acquire nuclear weapons. Although the specific circumstances occasioning nuclear weapons programs varies considerably, scholars have 4 Lawrence Freedman, The Evolution of Nuclear Strategy, 3rd ed (Houndmills, Basingstoke, Hampshire ; New York: Palgrave Macmillan, 2003),

9 nonetheless identified motives consistent across cases. 5 If states share reasons for developing nuclear weapons, one may also expect overlap in the dynamics driving force structure decisions, despite varied domestic constraints and threat environments. Understanding how external and internal factors influence decisions to develop particular platforms is important to understand how leaders conceptualize nuclear weapons as a tool of national power and provide insight into thinking about deterrence. Identifying key drivers of nuclear portfolio diversification has critical policy implications and can help to prevent both vertical and horizontal proliferation while simultaneously reducing the risk of state use of nuclear weapons. This study combines quantitative and qualitative approaches to examine states decisions about nuclear force structure and delivery platforms after acquiring initial nuclear weapons capabilities. Following a review of the extant literature, three main hypotheses for nuclear portfolio diversification based on affordability, survivability, and usability are proposed and tested. Statistical evidence for these hypotheses is inconclusive, and this led me to qualitatively evaluate particular cases that aligned with my theoretical expectations. The cases of the United States in the 1960s and early 1970s and Pakistan since 1998 model the survivability and usability hypotheses respectively. The US development of nuclear submarines enhanced a second-strike capability in the face of a growing Soviet 5 Dong-Joon Jo and Erik Gartzke, Determinants of Nuclear Weapons Proliferation, The Journal of Conflict Resolution 51, no. 1 (February 1, 2007): ; Erik Gartzke and Matthew Kroenig, Nuclear Posture, Nonproliferation Policy, and the Spread of Nuclear Weapons, Journal of Conflict Resolution 58, no. 3 (April 1, 2014): , doi: / ; Cirincione, Bomb Scare; Scott D. Sagan, The Causes of Nuclear Weapons Proliferation, Annual Review of Political Science 14, no. 1 (2011): , doi: /annurev-polisci

10 nuclear threat. Pakistan s doctrinal revisions and development of tactical platforms following conventional military defeats at the hands of India illustrates a desire to make its arsenal more usable and better suited to deter across the spectrum of conflict. 6 The fact that dynamics expected by my hypotheses are observable in historical cases suggests that the lack of solid quantitative evidence may stem from the limited number of observations across a small group of countries. Quantitative vs. Qualitative Methods Historically, studies of nuclear weapons have evaluated particular cases with emphasis on the nuclear arsenals and strategies of the Soviet Union and United States within the context of the Cold War. This qualitative approach makes a good deal of sense when working with a small number of nuclear powers over a short period of observation for nuclear security relative to other phenomena of international relations. But a recent renaissance in nuclear studies has also included quantitative studies of nuclear issues from proliferation to the role of nuclear weapons in crisis bargaining. 7 These studies seek to examine the behavior of all nuclear powers and identify commonalities across cases. Critics of the quantitative approach argue that the context and case dependency of interactions between nuclear powers and the limited number of observable cases makes statistical analysis ill-suited to study these issues 6 Narang, Nuclear Strategy in the Modern Era: Regional Powers and International Conflict, Erik Gartzke and Dong-Joon Jo, Bargaining, Nuclear Proliferation, and Interstate Disputes, The Journal of Conflict Resolution 53, no. 2 (April 1, 2009): ; Kyle Beardsley and Victor Asal, Nuclear Weapons as Shields, Conflict Management and Peace Science 26, no. 3 (July 1, 2009): , doi: / ; Jo and Gartzke, Determinants of Nuclear Weapons Proliferation. 10

11 These critiques fall within broader interdisciplinary and intra-disciplinary debates concerning the relative merits of quantitative and qualitative analysis. 8 Historians have sought to study nuclear weapons almost entirely qualitatively giving in-depth attention to the particularities of each nuclear power. Within the field of political science scholars remain divided on whether quantitative analyses are appropriate for study of nuclear weapons and other developments with a limited number of available observations. The use of statistical methods to gain insight and understand human behavior and societal, political and security dynamics is not new, but the increasing availability and quality of data has accelerated this process and allowed for greater sophistication in quantitative analysis. Critics concerns about the limitations of quantitative analysis certainly need to be addressed, especially given the gravity and potential consequences of flawed judgment in nuclear affairs. While I will defend my particular coding decisions and methods later in my chapter on research design and in the data appendix, a brief case for the use of quantitative analysis alongside qualitative studies is appropriate here. There is some danger in assuming that current circumstances are identical to previous events and that previously successful policies will guarantee a resolution of the issue. As the oft-quoted Mark Twain once quipped, History doesn t repeat itself, but it often rhymes. This sentiment reflects the need for both quantitative and qualitative study in the area of nuclear issues and strategic studies more broadly. It is problematic to assume every case and challenge faced is entirely unique and that lessons from history 8 For a more detailed explanation of the quantitative vs. quantitative debate in nuclear issues see: George Fujii, What We Talk About When We Talk About Nuclear Weapons, H-Diplo, June 15, 2014, 11

12 cannot be applied to current situations. Rather than simply looking for singular analogues to current events, studying a range of previous events can better provide inferences that inform the decisions of policymakers, even if the findings from these studies do not definitively determine a course of action in response to specific policy questions. Using a larger number of observations helps to highlight patterns and consistencies across different scenarios and can also illustrate the relative success of varied responses and actions in similar situations. Just as important as identifying similarities is finding the differences in conditions across various cases, looking at a number of observations allows this in a way that analysis of a singular event or direct comparison of just two events cannot. Working with a larger sample size improves our ability to make inferences about trends and occurrences in international affairs and the role of nuclear weapons therein. This is not to say that qualitative studies of particular periods or events are without merit. It is often helpful to think through problems and explain concepts through specific narrratives and carefully researched case studies are particularly helpful to illustrate the dynamics at play and help to give substance and shape to trends observed in statistical analysis. Furthermore, it is dangerous to treat quantitative studies and findings as authoritatively predictive of what will occur. Understanding how the differences of specific cases impacted historical events and led to divergent outcomes is also valuable. Using either quantitative or qualitative methods in isolation faces severe limitations, but using both in conjunction can improve understanding of the dynamics at play in the international system and how nuclear weapons affect these interactions. The existing empirical work on nuclear security has generally treated nuclear weapons as a dichotomous variable where the possession of a single nuclear bomb is 12

13 equivalent to an arsenal of over a thousand warheads. 9 Recently, scholars have begun to question assumptions made based on a binary measure of possessing or not possessing nuclear weapons despite wide variation in nuclear capabilities and arsenal size of different nuclear powers and across time. 10 It seems doubtful that a small nuclear power such as North Korea with a handful of nuclear weapons has the same deterrent effect and factors into other states decision-making the same way as the comparatively vast arsenals of the United States and Russia impact other states perceptions. This has led some scholars to begin evaluating different characteristics of nuclear arsenals and their effects. These studies have investigated the size of nuclear arsenals, the diversity of platforms and has also linked different platforms and capabilities to operational doctrine and force posture. 11 Parsing out distinguishing characteristics of force structures and doctrine enables a more thorough understanding of state-level nuclear decision-making as well as how these decisions impact international security. 12 These studies are important first steps in treating nuclear weapons with greater nuance and attempting to identify trends across nuclear powers. 9 Vipin Narang, What Does It Take to Deter? Regional Power Nuclear Postures and International Conflict, Journal of Conflict Resolution 57, no. 3 (June 1, 2013): , doi: / ; Narang, Nuclear Strategy in the Modern Era: Regional Powers and International Conflict. 10 Jeffrey Kaplow, Erik Gartzke, and Rupal Mehta, Nuclear Deterrence and the Structure of Nuclear Forces (ISA Annual Convention, San Francisco, CA, 2013), 11 Gartzke and Jo, Bargaining, Nuclear Proliferation, and Interstate Disputes ; Narang, What Does It Take to Deter? ; Curtis S. Signorino and Ahmer Tarar, A Unified Theory and Test of Extended Immediate Deterrence, American Journal of Political Science 50, no. 3 (July 1, 2006): ; Kaplow, Gartzke, and Mehta, Nuclear Deterrence and the Structure of Nuclear Forces. 12 Kaplow, Gartzke, and Mehta, Nuclear Deterrence and the Structure of Nuclear Forces ; Narang, Nuclear Strategy in the Modern Era: Regional Powers and International Conflict. 13

14 However, further work and evaluation of states decisions regarding nuclear force structures can help support (or refute) recent findings and improve our understanding of the causes and consequences of states diversifying their nuclear portfolio. Recent contributions from scholars such as Vipin Narang, Erik Gartzke, Jeffrey Kaplow, and Rupal Mehta, and others have enhanced our understanding of these decisions, but they have also identified areas for further study. This study helps to fill in some of these gaps and strengthens the growing body of quantitative work on nuclear issues by evaluating specific force structure decisions of states and their associated motives. Policy Significance Considerations of nuclear force structure remains an important policy issue for arms control efforts as well as the continued stability of deterrence outside of the Cold War strategic context. The United States and Russia are both now modernizing their nuclear arsenals and will hopefully engage in future arms reduction negotiations. Understanding how reductions in the overall size of an arsenal versus a reduction in the number of platforms or capabilities influences deterrence holds important implications for any future arms reductions efforts. 13 Alongside these concerns, the world continues to be confronted by the proliferation of nuclear technology and weapons to new states. Understanding how new nuclear powers may seek to structure their nuclear arsenal and what types of platforms signifies is crucial to responding to these new threats. As Russia and the United States decide how to modernize their nuclear arsenals, emerging and existing regional nuclear powers must decide how to structure their arsenal and what nuclear doctrine to employ to meet their strategic requirements. Enhancing 13 Kaplow, Gartzke, and Mehta, Nuclear Deterrence and the Structure of Nuclear Forces,

15 understanding of these emerging nuclear powers decisions can be invaluable. For instance, gaining insight into Pakistan and India s decisions about nuclear portfolio diversification and force posture may enable policymakers to reduce the risk of nuclear conflict between the rivals and potentially stem vertical proliferation in Pakistan. Developing a better understanding of how all states make these decisions, and in turn, how they influence deterrence is crucial to averting conflict at all levels, but is particularly important for reducing the risk of nuclear conflict. 15

16 Chapter 2: Literature Review The Nuclear Renaissance A recent surge in publications reflects renewed scholarly interest in nuclear weapons that has come to be described as a nuclear renaissance. 14 This attention follows a period of diminished prominence immediaately following the end of the Cold War in which the threat of nuclear exchange hung as a Sword of Damocles over both superpowers. 15 This new scholarship on nuclear proliferation and strategy exists within a very different strategic environment, one that Colin Gray and others have deemed the second nuclear age. 16 Much of this scholarship has focused on the causes of horizontal proliferation and has attempted to understand why and how states pursue nuclear weapons capabilities. 17 These scholars exploring the nuclear strategies and proliferation outside of the Cold War bipolar context and have wrangled with new questions about deterrence and nuclear strategy. This renaissance in nuclear security studies has also witnessed an increased use of quantitative methods to analyze nuclear trends and decision-making. This quantitative approach contrasts with traditional qualitative case study examinations of the nuclear programs and strategic thinking of specific states. Quantitative analysis has been applied 14 Adam N. Stulberg and Matthew Fuhrmann, eds., The Nuclear Renaissance and International Security (Stanford, California: Stanford Security Studies, an imprint of Stanford University Press, 2013). 15 Bureau of Public Affairs Department Of State. The Office of Website Management, Address by President John F Kennedy to the UN General Assembly, U.S. Department of State, September 25, 1961, 16 Colin S. Gray, The Second Nuclear Age (Boulder, Colorado: Lynne Rienner Publishers, 1999). 17 Beardsley and Asal, Nuclear Weapons as Shields ; Gartzke and Jo, Bargaining, Nuclear Proliferation, and Interstate Disputes ; Kyle Beardsley and Victor Asal, Winning with the Bomb, The Journal of Conflict Resolution 53, no. 2 (April 1, 2009): ; Gartzke and Kroenig, Nuclear Posture, Nonproliferation Policy, and the Spread of Nuclear Weapons ; Jo and Gartzke, Determinants of Nuclear Weapons Proliferation. 16

17 to causes of proliferation both from supply and demand side perspectives, the deployment of weapons abroad, to exploring the contours of deterrence and assessing impact of nuclear weapons on international crisis bargaining and resolution. 18 However, most of this study has concentrated on trends and issues in horizontal proliferation and its impact on international security, comparatively fewer studies have attempted to understand the effects of vertical proliferation. 19 The development of nuclear delivery platforms and the motivations for diversifying these portfolios has been described frequently in studies of specific states programs but has garnered less attention from quantitative scholars. 20 Catalogues of Delivery Platforms Numerous sources describe the current delivery platforms of the nine nuclear weapons states, and several serials such as the Bulletin of Atomic Scientists Nuclear Notebook, the International Institute for Strategic Studies Military Balance, the Stockholm International Peace Research Institute s Yearbook and Jane s Strategic Weapons Systems all describe states current s arsenals and are updated annually. 21 These compilations are based on open-source, unclassified information on nuclear programs and 18 Beardsley and Asal, Nuclear Weapons as Shields ; Matthew Fuhrmann and Sarah E. Kreps, Targeting Nuclear Programs in War and Peace: A Quantitative Empirical Analysis, , The Journal of Conflict Resolution 54, no. 6 (December 1, 2010): ; Matthew Fuhrmann and Todd S. Sechser, Signaling Alliance Commitments: Hand-Tying and Sunk Costs in Extended Nuclear Deterrence, American Journal of Political Science 58, no. 4 (October 1, 2014): , doi: /ajps.12082; Matthew Fuhrmann, Atomic Assistance: How Atoms for Peace Programs Cause Nuclear Insecurity, Cornell Studies in Security Affairs (Ithaca: Cornell University Press, 2012); Matthew Kroenig, Exporting the Bomb: Technology Transfer and the Spread of Nuclear Weapons, Cornell Studies in Security Affairs (Ithaca, [N.Y.]: Cornell University Press, 2010). 19 Gartzke, Kaplow, and Mehta, The Determinants of Nuclear Force Structure. 20 Ibid. 21 Stockholm International Peace Research Institute, Annual Yearbook (London, England: Oxford University Press, 1968z); Robert S. Norris and Hans M. Kristensen, Bulletin of the Atomic Scientists, Nuclear Notebook, (2000), The Military Balance, vol (International Institute for Strategic Studies, 1961). 17

18 have some degree of ambiguity about the number of weapons, platforms and dates deployed, but taken together as consolidated accounts of current nuclear and conventional capabilities they provided invaluable information for constructing the dataset used in my analysis. However, these are these are mainly catalogs of systems lacking narrative depth or full descriptions of states motivations behind developing particular platforms. State Specific Studies of Force Structure In-depth accounts of specific states delivery platforms can be found in a range of studies based on unclassified information available on nuclear forces. A greater number of studies have examined the programs of the United States, United Kingdom, France, South Africa, and the former Soviet Union and now Russia. Though many aspects of these countries nuclear programs remains subject to debate these studies have benefited from the relative transparency regarding these countries nuclear arsenals and doctrines. Chuck Hansen s U.S. Nuclear Weapons: A Secret History and Norman Polmar and Robert S. Norris The U.S. Nuclear Arsenal: A History of Weapons and Delivery Systems since 1945 are two of the most prominent and comprehensive studies of U.S. delivery platforms. 22 Stephen Blank s Russian Nuclear Weapons: Past, Present and Future and Pavel Podvig s Russian Strategic Nuclear Forces describe key developments in Russian delivery platforms. 23 Frank Barnaby and Douglas Holdstock s The British Nuclear Weapons Programme, and Kristan Stoddart s Losing an Empire and Finding a Role both describe key episodes and trends in the United Kingdom s 22 Chuck Hansen, U.S. Nuclear Weapons the Secret History (Arlington, TX : New York, N.Y: Crown, 1988); Norman Polmar and Robert S. Norris, The U.S. Nuclear Arsenal: A History of Weapons and Delivery Systems since 1945 (Annapolis, MD: Naval Institute Press, 2009). 23 Stephen Blank, Russian Nuclear Weapons : Past, Present, and Future (Carlisle, PA: Strategic Studies Institute, U.S. Army War College, 2011); Pavel Podvig, ed., Russian Strategic Nuclear Forces (Cambridge, MA: MIT Press, 2004). 18

19 development of nuclear weapons systems. 24 A look into South Africa s nuclear program including decisions about force structure and platforms can be found in Al Venter s How South Africa Built Six Atom Bombs. 25 Each of these works serves as helpful reference material for examining specific countries arsenals, but treating each country as a unique case and not trying to identify cross-country similarities is a missed opportunity that can be better exploited by combining quantitative and qualitative approaches. Scholars attempting to describe the force structures of China, India, Pakistan, and Israel have had to contend with much greater opacity surrounding all aspects of these countries programs. Despite these obstacles numerous scholars have put together impressive studies of these states nuclear force structures and doctrines. For coverage of India s nuclear delivery systems Ashley Tellis India s Emerging Nuclear Posture, George Perkovich s India s Nuclear Bomb, and Verghese Koithara s Managing India s Nuclear Forces provide excellent background. 26 Feroz Khan s Eating Grass: The Making of the Pakistani Bomb and Kamal Matinuddin s The Nuclearization of South Asia both include discussions of Pakistani development and deployment of delivery vehicles, namely aircraft and ground based missiles. The most comprehensive coverage of Israel s unacknowledged nuclear program is found in Avner Cohen s Israel and the Bomb and 24 Douglas Holdstock and Frank Barnaby, eds., The British Nuclear Weapons Programme, (London ; Portland, OR: Frank Cass, 2003); Kristan Stoddart, Losing an Empire and Finding a Role: Britain, the USA, NATO and Nuclear Weapons, , Nuclear Weapons and International Security since 1945 (Houndmills, Basingstoke, Hampshire ; New York: Palgrave Macmillan, 2012). 25 Al J. Venter, How South Africa Built Six Atom Bombs and Then Abandoned Its Nuclear Weapons Program (Kyalami Estate [South Africa]: Ashanti, 2008). 26 Verghese Koithara, Managing India s Nuclear Forces, 1 edition (Washington, D.C: Brookings Institution Press, 2012); George Perkovich, India s Nuclear Bomb: The Impact on Global Proliferation, First Edition, Updated Edition with a New Afterword edition (Berkeley: University of California Press, 2001); Ashley Tellis, India s Emerging Nuclear Posture: Between Recessed Deterrent and Ready Arsenal (Santa Monica, CA: RAND Corporation, 2001). 19

20 The Worst-Kept Secret: Israel s Bargain with the Bomb. 27 Each of these studies provide important insight into the trends of individual states nuclear programs and arsenals, but again they generally fail to identify commonalities across different nuclear weapons states or help predict the behavior of currently developing powers or potential future nuclear powers. Systematically comparing the varied decisions of the different de jure and undeclared nuclear states can better illustrate common trends that transcend idiosyncratic characteristics of individual states military structures or nuclear enterprises. Quantitative Studies One of the few systematic evaluations at nuclear force structure diversification across all de jure and de facto nuclear states is Erik Gartzke, Jeffrey Kaplow and Rupal Mehta s Determinants of Nuclear Force Structure. This study evaluates twelve hypotheses attempting to explain different states decisions to diversify and develop particular platforms between Gartzke et al. seek to answer why states choose to diversify their nuclear portfolio. They introduce a theory of portfolio diversification based on the total number of platforms deployed and seek to explain states motives to diversify their delivery capabilities. Gartzke et al. s hypotheses can broadly be broken into: 1) domestic constraints such as resource constraints and domestic and bureaucratic politics and 2) external factors such as the force structures and actions of conventional and nuclear rivals or allies. 27 Avner Cohen, Israel and the Bomb (New York: Columbia University Press, 1998); Avner Cohen, The Worst-Kept Secret: Israel s Bargain with the Bomb (New York: Columbia Univ. Press, 2010). 28 Gartzke, Kaplow, and Mehta, The Determinants of Nuclear Force Structure. 20

21 Vipin Narang s Nuclear Strategy in the Modern Era dovetails with Gartzke et al. s study and concentrates on the relationship between nuclear postures and deterrence in the post-cold War strategic landscape. 29 Instead of looking at platforms deployed and focusing on the portfolio of capabilities Narang codifies and develops a framework for understanding the effectiveness of deterrence for different nuclear force postures. Narang defines these postures as a fusion of capabilities and operational doctrine. Narang s study goes a long way to identifying the different decisions states make about their nuclear arsenals and strategy. As Narang argues, this provides greater insight than studies that simply treat nuclear power as a dichotomous variable where a state either possesses nuclear weapons or it does not but fails to fully examine the differences between possession of a handful of gravity bombs deliverable by aircraft and an arsenal such as Russia s comprised of nearly two dozen platforms with various yields and overall capabilities. This study builds on the findings of Narang and Gartzke et al. to further explore how states decide to develop particular platforms and what are the key motivations to diversify. As Gartzke et al. point out, diversifying systems can hold benefits for both the offensive and the defensive. Diversification can help to strengthen offensive capabilities by enabling states to develop systems to overcome defensive countermeasures, just as the development of ballistic and cruise missiles in the early 1960 s enabled the U.S. to overcome increasingly advanced Russian air defense systems or how the development of hypersonic glide vehicles threatens existing ballistic missile defense technologies. However, diversification is also beneficial for defensive reasons because different 29 Narang, What Does It Take to Deter? ; Narang, Nuclear Strategy in the Modern Era: Regional Powers and International Conflict. 21

22 systems may be less vulnerable to an adversary s first strike. A prime example of this is the development of nuclear submarines (SSBNs) that are largely immune to preemptive counterforce strikes. While Gartzke et al. acknowledge these dual benefits of diversification, their study fails to distinguish whether states diversify for offensive or defensive purposes. 30 Part of identifying whether states are attempting to strengthen their offensive is understanding whether the diversification of nuclear portfolios makes systems that are more usable, that is, weapons could be conceivably employed at lower thresholds or used in instances short of an all out nuclear exchanges. Contrarily, it is also possible that states decisions to diversify is not to strengthen the offensive or make their nuclear weapons more usable, but is instead primarily motivated by a desire to strengthen the survivability of their force and guarantee themselves a second-strike capability. To compare the dual motives of survivability versus usability, a more granular study of the capabilities of new systems developed is necessary. While Gartzke et al. s use of number of distinct platforms does measure diversification, it is insufficient to answer the questions of whether states diversify for offensive or defensive purposes. Developing systems with significantly different ranges and payloads or warheads with variable yields seems to indicate an offensive intent to make the arsenal more usable. This was reflected in the delivery vehicles developed when McNamara and Kennedy implemented their flexible response doctrine. 31 By contrast, deploying platforms such as SSBNs signifies an effort to ensure the survivability of a second-strike capability in the 30 Gartzke, Kaplow, and Mehta, The Determinants of Nuclear Force Structure, Freedman, The Evolution of Nuclear Strategy, 220 1,

23 event of a preemptive counterforce strike. Measuring the aggregate number of platforms fails to capture these nuances that signal very different postures for nuclear arsenals. Nuclear Strategic Schools of Thought Distinguishing between usability versus survivability of nuclear arsenals is closely linked to broader views on the utility of nuclear weapons. Although only two nuclear weapons have ever been used in wartime, different nuclear powers have developed a range of doctrines outlining the roles of nuclear weapons as tools of military power. Without delving into the intricacies of individual states doctrines, three schools of thought about the utility of nuclear weapons explain the theoretical underpinnings of present and historical nuclear doctrines.. The first and most popular is the nuclear revolution school of thought, contending that the incredible destructive capacity of nuclear weapons marks a revolution in warfare and that nuclear war is unwinnable. Proponents of this view argue that the only reason to hold nuclear weapons is to deter and ensure they are never used. Francis Gavin has called this the mutual vulnerability/strategic stability school that contends the guaranteed second-strike capabilities create a degree of strategic stability by removing the incentive for a first strike. 32 This logic underlies the doctrine of Mutually Assured Destruction (MAD) where a full-scale nuclear strike and a retaliatory strike would result in the annihilation of both adversaries. If nuclear weapons are conceptualized in this fashion the survivability of a state s arsenal should always be the paramount priority. 32 Francis J Gavin, Nuclear Statecraft: History and Strategy in America s Atomic Age. (Ithaca, [N.Y.]: Cornell University Press, 2015),

24 The damage limitation school, calls for development of a range of nuclear platforms with varied yields that can be used in a more limited fashion and are intended to deter across the spectrum of armed conflict. 33 The Kennedy administration s doctrine of flexible response epitomized this perspective of nuclear weapons and the US development of tactical platforms throughout the 1960s reflected this strategic thinking. The damage limitation strategy articulated by Henry Kissinger and others based on counterforce targeting emerged from this view of nuclear weapons as more or less another capability to be employed alongside conventional means. Thinkers within this school consider nuclear warfare winnable if waged in a limited fashion and if first-strike, counterforce capabilities are developed to ameliorate the effectiveness of any retaliatory strike. A third, more uncommon perspective considers utility for nuclear weapons as means of compellence through nuclear brinkmanship. The brinkmanship school believes that the threat of using nuclear weapons or pushing to the brink of nuclear war can compel an adversary to back down or alter their behavior. 34 Nuclear brinkmanship was reflected in the madman theory of President Nixon, who threatened both the Soviet Union and Vietnam with nuclear weapons. A modern analogue can be found in the posturing of North Korea under Kim Jong-Un, who has crafted the image of an irrational actor willing to use nuclear weapons against both South Korea and the United States. Although North Korea s current delivery capabilities remain limited their pursuit of intercontinental ballistic missiles (ICBMs) capable of striking the western United States and Kim s 33 Ibid., Ibid.,

25 perception as an irrational and aggressive dictator both demonstrate elements of brinkmanship. While platforms such as aircraft capable of being recalled can be useful within this brinkmanship strategy, this view of nuclear weapons is not as closely attached to a particular force structure as both the massive retaliation and damage limitation strategies. Because this strategy envisions preemptive first use, ensuring survivability is not a key priority. However, because this strategy relies on implied instability and irrationality of those in control of nuclear forces, it does not call for the same spectrum of capabilities to enhance the credibility of nuclear threats. As a consequence, it is much more difficult to link nuclear portfolio diversification to this view of nuclear weapons. The recent surge in scholarly interest in nuclear security has produced new quantitative and qualitative works on nuclear proliferation and its impact on international security. However, most of these works have either explored states motives for pursuing nuclear weapons or used the possession of nuclear weapons as an explanatory variable influencing interstate interactions. These studies have not evaluated nuclear force structure decisions after states acquire nuclear weapons, and they have not thoroughly examined the impacts of different diversified nuclear portfolios on international security. Extant literature specifically about nuclear delivery platforms is either case specific evaluating the diversification individual states arsenals or focusing on the technical details of platforms rather than the underlying motivations of diversification. Gartzke et al. s study offers the first systematic evaluation of states decisions to diversify nuclear portfolios. My analysis builds upon this work and attempts for understand the dynamics of diversification more fully by differentiating between the types of platforms 25

26 developed by nuclear powers. These force structure decisions are important because the mirror states and policymakers diverging views about the role of nuclear weapons as tools of national power. 26

27 Chapter 3: Theoretical Expectations Motives for Diversification States decisions to diversify their nuclear portfolio are influenced both by financial constraints and strategic considerations. First and foremost, a state must be able to afford the costs of development and have the technological base to develop particular platforms. Beyond these constraints, different platforms have distinct characteristics that enhance their usefulness for either offensive or defensive purposes. Understanding the types of platforms deployed can provide key insights into the intended purposes of states nuclear arsenals. The dual benefits of diversification for both offensive and defensive purposes point to the two primary motivations behind states decisions to diversify their nuclear portfolios through developing new warheads and especially new delivery vehicles. 35 First, diversification can serve as a defensive hedge to strengthen the survivability of a state s arsenal and guarantee a second-strike capability. Strengthening survivability and reliability of an arsenal is twofold. Diversification avoids overreliance on a single platform where a technical malfunction or error on a single system could render the entire arsenal impotent. 36 More importantly, deploying different systems and launchers and particularly concealable platforms reduces the vulnerability of a state s nuclear arsenal to an adversary s preemptive first strike. 37 Developing different platforms with varied capabilities improves a state s offensive nuclear capabilities and expands the manners in which warheads can be launched and the number of situations in which nuclear weapons 35 Gartzke, Kaplow, and Mehta, The Determinants of Nuclear Force Structure, Ibid., Freedman, The Evolution of Nuclear Strategy,

28 would be used. Do states diversify platforms to strengthen survivability or increase usability of their nuclear arsenals? Prioritizing either survivability or flexibility and usability reflect different schools of thought about nuclear weapons and as a consequence are also interlinked with notions of doctrine or stated force postures of various states. Emphasizing survivability is more consistent with a posture of assured retaliation and reflects the thinking of the nuclear revolution school arguing that all nuclear wars are unwinnable and the only reason to have nuclear warheads is to prevent their use. Focusing on expanding the type of capabilities, ranges, and yield of weapons and particularly the development of lower-yield tactical nuclear weapons suggests just the opposite and assumes that possessing a range of capabilities is critical to strengthen the credibility of nuclear deterrence even against lower thresholds of violence. These parallel reasons for diversification are not necessarily mutually exclusive, but the types of platforms deployed as states diversify can offer insight into which of these is a more powerful motive for diversification. Considerations of diversification should also look at the impetus for diversification, and identifying developments that lead states to diversify either for survivability or usability. Gartzke et al. identify nearly a dozen different potential determinants of force structure. This paper attempts to examine a couple of these explanatory variables while also disaggregating the types of platforms in greater detail. 28

29 Affordability, Survivability and Usability One of the key limitations on diversification is the costs necessary to develop and deploy new systems. As Gartzke et al. point out, developing nuclear weapons is an expensive proposition in and of itself, and those states able to develop these weapons have the economic wherewithal to develop new platforms. 38 They found a negative correlation between real GDP and number of platforms deployed, this fails to capture how states diversify across of types of platforms at varying levels of GDP and military expenditure. Because most states that develop nuclear weapons would already have various aircraft in their conventional armed forces that could potentially carry nuclear weapons, diversifying within the air leg of the triad would be the most cost effective for states facing economic constraints. More development of more expensive missile systems would occur with increased real GDP and higher levels of military expenditure. Affordability Hypothesis: Lower levels of real GDP and military expenditures will lead states to prioritize aircraft in their nuclear arsenal. Another key objective for some nuclear powers is diminishing vulnerability to a preemptive strike. The best way to strengthen an arsenal s survivability is to minimize an adversary s ability to observe and target warheads and platforms. Missiles launched from fixed positions (even those within hardened silos) are much easier targets than missiles or systems that are constantly moving and capable of being launched from a near infinite number of locations. Thus, the most survivable delivery vehicles are those that are mobile or capable of being positioned such that they are not easily observed or targeted by an adversary. Within the umbrella category of mobile launchers, submarine based missiles 38 Ibid.,