Alliance formation and war

This article provides a game-theoretic model of alliance formation and war. The model examines how alliances affect the behavior of states. Several aspects of the alliance literature are simultaneously incorporated into the model. The model endogenizes alliance reliability, the effect of alliance on the occurrence of war, and alliance formation. The results explain several empirical phenomena. Although alliance formation has predictable effects on the behavior of nations, the aggregate effect of alliances on the occurrence of war is ambiguous. Under some circumstances alliances increase the probability of war; in others, alliances reduce the likelihood of war. Alliance reliability affects the behavior of nations. Nations with unreliable alliances are more likely to be attacked than those with reliable alliances. How this sampling affects empirical estimates of alliance reliability is discussed. -Author