I consider a model in which two states choose how much to arm and whether to attack in successive periods. Arms are useful not only for deterrence or taking territory, but also because they influence the resolution of a set of disputed issues. It is shown that states can cooperate on the issues by limiting military competition, but only as far as a “war constraint” allows. Factors determining the tightness of the war constraint imply hypotheses about the international determinants of military eort and thus the costs of anarchy. The strategic logic of the model diers from standard security dilemma arguments, in which the costs of anarchy are associated with conflict between status quo states that are uncertain about others’ territorial revisionism. Here, ineciency arises because arming to deter lowers a state’s value for living with the status quo, which creates a security externality and a feedback loop. The model both synthesizes and revises a diverse range of theoretical arguments about the determinants of interstate cooperation and conflict.

James D. Fearon is Theodore and Frances Geballe Professor in the School of Humanities and Sciences and Professor of Political Science at Stanford University. He is also a Senior Fellow at the Freeman-Spogli Institute for International Studies. His research focuses on political violence – interstate, civil, and ethnic conflict in particular. In addition he has worked on aspects of democratic theory and the impact of democracy on foreign policy. He has published numerous articles in scholarly journals, including “How Does Development Assistance Affect Collective Action Capacity? Results from a Field Experiment in Post-Conflict Liberia” (co-authored with Macartan Humphreys and Jeremy Weinstein, in American Political Science Review), “Self-Enforcing Democracy” (Quarterly Journal of Economics), “Iraq’s Civil War” (Foreign Affairs), “Neotrusteeship and the Problem of Weak States” (co-authored with David Laitin, in International Security), “Ethnicity, Insurgency, and Civil War” (co-authored with David Laitin, in American Political Science Review), and “Rationalist Explanations for War” (International Organization). Fearon was elected member of the National Academy of Sciences in 2012 and the American Academy of Arts and Sciences in 2002. He has been a Program Fellow of the Canadian Institute for Advanced Research since 2004. He served as Chair of the Department of Political Science at Stanford from 2008-2010.