THE OFFENSE-DEFENSE BALANCE AND WAR SINCE 1648∗ James D. Fearon Department of Political Science University of Chicago 5828 S. University Ave. Chicago, IL 60615 email:
[email protected] DRAFT - April 8, 1997 ∗This is a slightly revised version of a paper presented at the Annual Meetings of the Inter- national Studies Association, Chicago, Illinois, 21-25 February 1995. For helpful comments and discussions I wish to thank David Edelstein, Charles Glaser, Chaim Kaufmann, and Craig Koerner. 1 Introduction In one of the most influential articles on international relations written in the last 25 years, Robert Jervis argued that technological, geographical, and political factors that render of- fensive operations less costly and more effective tend to make security competition fiercer and wars more likely.1 While the basic idea that technology favoring the offense might foster war and have diverse other international effects was not new,2 Jervis made a more coherent and thorough theoretical argument than had been offered previously, and supported it with a range of suggestive and plausible historical examples. Since “Cooperation under the Se- curity Dilemma,” many international relations scholars (and neorealists in particular) have added the “offense-defense balance” to system polarity as one of the chief independent vari- ables used to explain international outcomes, especially the occurrence of war. And possibly because polarity does not vary much over time, the offense-defense balance has been doing a lot of explanatory and theoretical work in recent realist writings on international politics.3 1Jervis, “Cooperation under the Security Dilemma,” World Politics30, 2 (January 1978), 167-214.