Military Coalitions and the Problem of Wartime Cooperation

Military coalitions are everywhere in international politics: deterring wars, waging wars (when deterrence fails), and enforcing (or tolerating) the peace that follows. Alex Weisiger’s recent ISQ article, “Exiting the Coalition,” studies the challenges of sustaining military cooperation during interstate wars, showing that coalition partners are more likely to pull out of the war effort when fighting separately from their partners and when things aren’t going well on the battlefield—two factors that make cooperation difficult to sustain even in the face of the side payments that often secure military cooperation. The contributors to this symposium, Marina Henke and Daniel Morey, engage Weisiger’s study by exploring the limits of specific coding rules and how they relate to underlying concepts of abandonment (versus, say, entrapment) and the extent to which a coalition’s aims are fixed (across either time or the membership). In his response, Weisiger notes that coding rules generally hold up to some specific objections, but he also argues that his key hypotheses should be robust even to the possibility that states try to compensate their partners to prevent abandonment when things go poorly on the battlefield.1  It’s a rich symposium on a topic that feels very present—especially as (a) coalition efforts continue against ISIL in Iraq and Syria and (b) the peacetime coalition that has managed the Postwar global order for over seven decades has begun to show some cracks in its foundations.

I’ll let the contributors’ comments and the author’s response stand on their own below, but I do think it worth mentioning that each piece in this symposium reflects a tension that all scholarship on coalitions must face: the lack of a common, shared idea of what constitutes a military coalition. Glenn Snyder noted twenty-six years ago that alliances are relatively easy to identity and describe, but coalitions less so. During wartime, we often think it’s easy to know them when we see them, but in the crises before the war and in the peacemaking and enforcement phase afterwards, it’s less clear.2  Operational definitions in prewar, wartime, and postwar phases abound (if you’ll pardon the self-promotion, see Chapter 2 here), yet even as Weisiger focuses quite reasonably on a clear, obvious environment—shared war efforts—the contributions to this symposium show that there’s still plenty of space to fill in describing the core elements of what it means to participate in a coalition, to build one, and to leave one. To be sure, as the contributors and others (here, here, here, and here, inter alia) have shown, states join military coalitions for different reasons and on different terms, and the terms of military cooperation must often be renegotiated as battlefield realities or war aims evolve. This requires that we think hard about integrating theories of military cooperation with theories of crisis bargaining, of war prosecution and termination, and of restoring peace after wars end. Engaging in debates like this, which will allow us to work out a few agreed features of the object under study, not only when deterrence fails and coalitions go to war but also when they pursue their aims short of war and when they try to manage their victories, will ultimately prove useful for identifying the role of military coalitions in both war-time and peacetime.


1 Which presumably implies that the relationships uncovered in the observational data underestimate the true relationships, because a number of defections that would’ve occurred are now kept off the equilibrium path by compensation schemes. But I digress.
2 Alliances, of course, are one solution to that problem, as they try to clarify who will and won’t be part of wartime coalitions. But they’re neither necessary nor sufficient for us to see a coalition form in practice.

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