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The Perils o f proliferation Organization Theory, Deterrence Theory, and the Spread of Nuclear Weapons Scott D. Sagan A n apparent contradiction lies at the center of our understandings about nuclear weapons and deterrence. On the one hand, it is widely believed that nuclear weapons were an important factor in maintaining the ”long peace” between the United States and the Soviet Union during the Cold War. The two superpowers avoided war despite a deep geopolitical rivalry, repeated crises, and a prolonged arms race. On the other hand, it is also widely believed that the continuing spread of nuclear weapons will greatly increase the risks of nuclear war. New nuclear powers, with similar characteristics of rivalry, are considered unlikely to maintain stable deterrence. A prominent group of political scientists have pointed to the apparent contradiction between a peaceful nuclear past and a fearful nuclear future and argue that the further spread of nuclear weapons will be a stabilizing factor in international relations. Kenneth Waltz’s 1981 monograph-The Spread of Nuclear Weapons: More May Be Better-presented the first detailed and forceful set of arguments in favor of proliferation.’ Since that time, however, a significant number of rational choice and neorealist political scientists have jumped onto the pro-proliferation bandwagon. Bruce Bueno de Mesquita and William Riker advocate spreading nuclear weapons into areas where non-nuclear states face nuclear-armed adversaries since ”the chance of bilateral conflict becoming nuclear . . . decreases to zero when all nations are nuclear armed.‘’2 John Mearsheimer believes that ”nuclear weapons are Scotf D. Sagaii is Assistant Professor of Political Screrzce at Stanford Uniuersity. For helpful comments I thank Richard Betts, George Bunn, Michael Desch, Lynn Eden, Peter Feaver, Neil Joeck, John Mearsheimer, George Perkovich, William Potter, and Jessica Stern. Financial support was provided by the Nuclear History Program and Stanford’s Center for International Security and Arms Control. 1. Kenneth N. Waltz, Tlze Sprend of Nuclear Weqmris:More Mny Be Better, Adelphi Paper No. 171 (London: International Institute for Strategic Studies [IISS], 1981). 2. Bruce Bueno de Mesquita and William H. Riker, ”An Assessment of the Merits of Selective Nuclear Proliferation,” lourid of Conflicf Xesolrttion, Vol. 26, No. 2 (June 1982), p. 283. Also see Bruce Bueno de Mesquita, ”Nuclear Peace Through Selective Nuclear Proliferation” (unpublished manuscript, the Hoover Institution, Stanford University, 1987). [iifrmnfiorzalSecurify, Vol. 18, No. 4 (Spring1994), pp. 66-107 Q 1994 by the President and Fellows of Harvard College and the Massachusettslnstitute of Technology. 66 The Perils of Proliferation I 67 a superb deterrent” and argues that both Germany and Ukraine should be encouraged to become nuclear powers in the post-Cold War era.3 Other neorealist scholars reach similar conclusions: Stephen Van Evera calls for German acquisition of a nuclear arsenal to deter Russia; Barry Posen recommends that Ukraine should keep nuclear weapons as a deterrent against Russian military intervention; Peter Lavoy predicts that nuclear weapons will prevent future wars between India and Pakistan; and Shai Feldman argues that nuclear proliferation in the Middle East can stabilize the Arab-Israeli ~onflict.~ The logic of this ”proliferation optimist” position flows easily from the expected-utility assumptions of rational deterrence theory: the possession of nuclear weapons by two powers reduces the likelihood of war precisely because it makes the costs of war so great. Such optimistic views of the effects of nuclear proliferation have not escaped criticism, of course, and a number of scholars have argued that nuclear deterrence may not be stable in specific regional setting^.^ What is missing 3. In 1990, Mearsheimer argued that ”Europe will be more stable if Germany acquires a secure nuclear deterrent, but proliferation does not go beyond that point.” In 1993, he amended his prescription: ”the best formula for maintaining stability in post-Cold War Europe is for all the great powersincluding Germany and Ukraine-to have secure nuclear deterrents.” John J. Mearsheimer, “Back to the Future: Instability in Europe After the Cold War,” International Security, Vol. 15, No. 1(Summer 1990),pp. 5-56 (quotations at p. 20 and p. 8);and Mearsheimer, ”The Case for a Ukrainian Nuclear Deterrent,” Foreign Affairs, Vol. 72, No. 3 (Summer 1993), pp. 50-66 (quotation at p. 51). In...