Summary

Military alliances predate even the state system as a form of international cooperation, and they take on many forms. The motivations of states seeking to join, the commitment levels formalized in the alliance agreement, and degrees of institutionalization all take different forms in the literature, but these scholarly perspectives can be boiled down to a few approaches: the realist, the rationalist and formalist, the liberal or institutionalist, and finally, the constructivist arguments on alliance identities. Moreover, a common thread among the literature on military alliances is an understanding that alliances provide a wide range of services to their members, and contain more than one motivation for forming and maintaining the alliances. Given that the motivations for forming alliances are varied, especially during different threat environments, it is important to ask what the consequences are. In this vein, scholars consider two primary issues: if these alliances can fulfill their intended missions, and if there are unintended consequences which may arise and lead to undesirable results. A related issue to the study of what motivates alliances is in how well they perform in terms of cohesion. Cohesion is, roughly speaking, the capacity of an alliance to effectively carry out its goals. Finally, there are the coalitions—ad hoc multinational understandings that are forged to undertake a specific mission, and dissolve once that mission is complete. They are not wholly analytically distinct from wartime alliances, although the latter may have a greater degree of institutionalization and may predate a specific wartime operation.