The Stability of a Unipolar World

The Stability of a Unipolar World William C. Wohlforth The collapse of the Soviet Union produced the greatest change in world power relationships since World War II. With Moscow’s headlong fall from superpower status, the bipolar structure that had shaped the security policies of the major powers for nearly half a century vanished, and the United States emerged as the sole surviving superpower. Commentators were quick to recognize that a new “unipolar moment” of unprecedented U.S. power had arrived.1 In 1992 the Pentagon drafted a new grand strategy designed to preserve unipolarity by preventing the emergence of a global rival.2 But the draft plan soon ran into controversy, as commentators at home and abroad argued that any effort to preserve unipolarity was quixotic and dangerous.3 Ofªcials quickly backed away from the idea and now eschew the language of primacy or predominance , speaking instead of the United States as a “leader” or the “indispensable nation.”4 The rise and sudden demise of an ofªcial strategy for preserving primacy lends credence to the widespread belief that unipolarity is dangerous and unstable. While scholars frequently discuss unipolarity, their focus is always on its demise. For neorealists, unipolarity is the least stable of all structures because any great concentration of power threatens other states and causes them to take action to restore a balance.5 Other scholars grant that a large International Security, Vol. 24, No. 1 (Summer 1999), pp. 5–41© 1999 by the President and Fellows of Harvard College and the Massachusetts Institute of Technology. William C. Wohlforth is Assistant Professor of International Relations in the Edmund A. Walsh School of Foreign Service at Georgetown University. I am indebted to Stephen G. Brooks, Charles A. Kupchan, Joseph Lepgold, Robert Lieber, and Kathleen R. McNamara, who read and commented on drafts of this article. 5 1. Charles Krauthammer, “The Unipolar Moment,” Foreign Affairs, Vol. 70, No. 1 (Winter 1990/1991), pp. 23–33. 2. Patrick Tyler, “The Lone Superpower Plan: Ammunition for Critics,” New York Times, March 10, 1992, p. A12. 3. For the most thorough and theoretically grounded criticism of this strategy, see Christopher Layne, “The Unipolar Illusion: Why New Great Powers Will Arise,” International Security, Vol. 17, No. 4 (Spring 1993), pp. 5–51; and Layne, “From Preponderance to Offshore Balancing: America’s Future Grand Strategy,” International Security, Vol. 22, No. 1 (Summer 1997), pp. 86–124. 4. The phrase—commonly attributed to Secretary of State Madeleine Albright—is also a favorite of President Bill Clinton’s. For example, see the account of his speech announcing the expansion of the North Atlantic Treaty Organization in Alison Mitchell, “Clinton Urges NATO Expansion in 1999,” New York Times, October 23, 1996, p. A20. 5. Kenneth N. Waltz, “Evaluating Theories,” American Political Science Review, Vol. 91, No. 4 (December 1997), pp. 915–916; Layne, “Unipolar Illusion”; and Michael Mastanduno, “Preserving concentration of power works for peace, but they doubt that U.S. preeminence can endure.6 Underlying both views is the belief that U.S. preponderance is fragile and easily negated by the actions of other states. As a result, most analysts argue that unipolarity is an “illusion,” a “moment” that “will not last long,” or is already “giving way to multipolarity.”7 Indeed, some scholars question whether the system is unipolar at all, arguing instead that it is, in Samuel Huntington’s phrase, “uni-multipolar.”8 Although they disagree vigorously on virtually every other aspect of post– Cold War world politics, scholars of international relations increasingly share this conventional wisdom about unipolarity. Whether they think that the current structure is on the verge of shifting away from unipolarity or that it has already done so, scholars believe that it is prone to conºict as other states seek to create a counterpoise to the overweening power of the leading state. The assumption that unipolarity is unstable has framed the wide-ranging debate over the nature of post–Cold War world politics. Since 1991 one of the central questions in dispute has been how to explain continued cooperation and the absence of old-style balance-of-power politics despite major shifts in the distribution of power.9...