Choosing Sides: The Dynamics of Coalitions

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In the fall of 2006 Sunni tribes turned on Al Qaeda in Iraq and allied with the United States. This - along with the surge in American troops and a change in American strategy - reversed the course of the insurgency. Alignment decisions and coalition dynamics are often key factors in determining the outcome of civil and interstate wars. Yet theoretical work done over the last two decades on the causes and conduct war of has very little to say about coalitions. This work has made very important insights. But it has almost exclusively focused on two-actor models. Building on that literature, this project attempts to extend the insights derived from two-actor models of war to the formulation and analysis coalitions. These include a third party's decision of whether and how to intervene in a war of attrition; the role of third parties in proxy wars; a general model of divide and conquer, and the centripetal forces that tend to break coalitions apart as they near their goals. A main result of this project will be a clearer conceptual foundation for empirical efforts to estimate the effects of third-party intervention in civil wars. Looking to the broader impacts of the project, the United Nations High Commission for Refugees recently reported that there were nearly 60 million displaced people in 2014, half of them children (New York Times, 18 June 2015). Civil war was a major cause. A clearer understanding of coalition dynamics may be a small step toward mitigating these effects.Alignment decisions and coalition dynamics are often key factors in determining the outcome of civil and interstate wars. Yet the formal, game-theoretic work done on the causes and conduct of war in the twenty years since Fearon's "Rationalist Explanations of War" (1995) has largely focused on two-actor games, often on two-actor bargaining games. This work is largely silent on coalitional issues. Building on that literature, this project attempts to extend the insights derived from two-actor models of war to the formulation and analysis of models coalitional dynamics in the shadow of conflict. More specifically, the goal of this project is to identify and analyze broad, canonical problems in coalition formation and then formalize them as "workhorse" models. Preliminary work has already analyzed the problem facing a third party in deciding whether to take sides in a war of attrition. Two-actor wars of attrition are commonly used to model many different kinds of conflict, including civil wars. Thought of as all-pay, second-price auctions, wars of attrition have been generalized to allow for n players competing for n-k prizes (Bulow and Klemper 1999). Surprisingly, however, no one has previously analyzed the very natural question of what a third party would do when it has preferences over who wins the war of attrition and can influence that outcome by supporting one side or the other. This project will first extend and generalize the preliminary results of the analysis of the model of choosing sides in a war of attrition. The project will then formulate other coalitional problems like divide and conquer (or rule), and the centripetal forces that tend to break coalitions apart as they near their goals.