Nothing to Fear but Fear Itself? Nuclear Proliferation and Preventive War∗ Alexandre Debsy and Nuno Monteiroz November 5, 2010 Abstract When does nuclear counterproliferation succeed? When does it lead to preventive war? We argue that the answers to these questions hinge on the effect of nuclearization on the balance of power relative to the cost of preventive war. When it is low, threats of preventive war are not credible; proliferation continues apace and peace prevails. Such was the case during the Cold War. When it is high, threats of preventive war are credible, slowing down the rate of proliferation. At the same time, since the decision to proliferate is not perfectly observable, there is a higher likelihood of mistaken preventive wars. This characterizes the post Cold War. We trace the logic of our argument by looking at the cases of Soviet nuclear acquisition in 1949 and the US-led invasion of Iraq in 2003. Keywords: deterrence, nuclear weapons, power, preventive war, proliferation. ∗We thank Jonathan Caverley, Jonathan Kirshner, Andrew Kydd, Barry Posen, Andrew Ross, Joshua Rovner, Bruce Russett, Duncan Snidal, workshop participants at Cornell, Madison, MIT, and Yale, and audiences at the ISSS/ISAC and PSS annual meetings for their comments and suggestions; and Will Bruno, Bonny Lin, and Hayden Stein for their research assistance. yDept. of Political Science, Yale University. Email:
[email protected] zDept. of Political Science, Yale University. Email:
[email protected] 1 1 Introduction In October 2002, pressing the case for invading Iraq, President Bush warned of terrible con- sequences should Saddam Hussein acquire nuclear weapons.