Keeping Your Friends Close, but Acquaintances Closer: Why Weakly Allied States Make Committed Coalition Partners

Why do states join wartime coalitions despite the absence of a salient threat or strong ties to the coalition leader? We argue states make unexpectedly high contributions to coalition warfare as a costly signal of their desire for a stronger relationship with the coalition leader. Conventional theories insufficiently explain why states without immediate security interests or strong ties to the lead state over-contribute relative to their capacity. Using newly compiled data on troop contributions to the war in Afghanistan (2001–2014), we find states are most likely to contribute a higher share of their armed forces when their relationship with the US has unrealized alliance potential. States with under-performing alignments leave substantial room for subsequent gains to be had from signaling their commitment to the leading coalition actor. Our finding helps explain why states risk the costs of war—casualties and domestic accountability—by participating in coalition warfare.

Centralized command and coalition victory

Building upon research that found that coalitions are more likely to win wars, recent work has sought to differentiate effective from ineffective coalitions. Much of this work focuses on characteristics of member states and not the coalition itself. This paper takes a first step in exploring how the structure of a coalition contributes to its performance. Specifically, coalitions vary in how much control members must transfer to the coalition. Some coalitions form weak command structures with states maintaining primary control while other coalitions form a strong centralized command. The impact of command structure on coalition performance is vital to understanding the success and failure of coalitions. Highly centralized command structures allow states to overcome the problems associated with coalition warfare and achieve victory. Empirical evidence supports this claim; the odds of victory increase as states surrender more control to the coalition. These findings provide direct advice to policy makers considering forming a coalition. The implications of this research extend to the alliance literature and the war bargaining literature, which tend to assume either that wars are dyadic or that states can seamlessly aggregate military capabilities.

Supplying Allies: Political Economy of Coalition Warfare

We outline a framework for understanding variation in cobelligerent resource coordination of money and material. An important feature of coalitional resource procurement is the role played by private firms and market forces. These shape the processes by which cobelligerents facilitate acquisition and distribution. At times, cobelligerents rely on themselves or the unilateral provision of resources from a major power supplier. At other times, cobelligerents pool their resources and create international institutions to coordinate the purchase of material. Our framework demonstrates that to understand the means by which coalitions supply themselves and, in turn, create wartime efficiencies in money and material, one must account for both classic determinants of alliance politics—namely the distribution of power between allies—as well as domestic and transnational market forces that can constrain or enable coalition members’ ability, individually and collectively, to procure war inputs.