Collective Deterrence in the Shadow of Shifting Power

Abstract

AbstractTwelve of twenty-six war-winning coalitions since 1815 have seen at least two members go to war against one another after victory. What separates durable and fragile war-winning coalitions? To answer this question, we analyze a game-theoretic model of shifting intra-coalition power and collective deterrence. We show that (1) shifting power within war-winning coalitions can undermine commitments to the postwar settlement, but (2) revisionist threats from a powerful defeated side can enhance the credibility of commitments within the winning coalition, securing peace when intra-coalition war would otherwise be inevitable. We also recover these patterns in empirical models of the outbreak of war between former coalition partners: shifting power within a coalition is associated with increased probabilities of intra-coalition war, but only when the defeated side is not too powerful. A common enemy can thus preserve peace between former partners who would otherwise go to war over the terms of shared victory.