Designing Alliances: How adversaries provoke peacetime military coordination

States form military alliances for the security benefits they provide. Despite this common purpose of military alliances, alliances vary a great deal in their design. Notably, some states form alliances that involve extensive peacetime military coordination while others form alliances with minimal peacetime military coordination. I argue that this variation in alliance design is motivated by the bargaining power of any challengers the members face. When a state faces a relatively weak challenger it will not have an incentive to pay the greater cost associated with a high level of peacetime coordination because a low level of peacetime military coordination will deter the challenger. However, if a state faces a relatively strong challenger a low level of peacetime military coordination will fail to deter the challenger and, thus, it will be willing to pay the additional costs associated with a high level of peacetime military coordination. An empirical analysis of the design of alliances from 1816 to 2001 supports hypotheses derived from the argument. The findings highlight how the design of alliances is driven, in part, by the characteristics of nonmembers.