Strategic (Under) Militarization in Alliances

• In Event: Formal Models of Conflict

Abstract

Alliances are often seen as a tool to deter attacks from potential aggressors. However, from the standpoint of potential aggressors, it is rarely a foregone conclusion that stronger allies would for sure come to the rescue of weaker states, if such weaker states were to be attacked. How should weaker states behave? We develop a model of militarization in alliances, where a weaker country is in an ambiguous military alliance with a stronger one, and relies on the stronger ally to deter challenges from an aggressor. The reliability of the alliance is private information of the allies, whereas the aggressor is uncertain about it. The weaker state needs to invest enough in military capacity so that an intervention of the stronger ally in its defense would be enough to defeat the aggressor. However, we show that the weaker country will limit its investment in its own military capacity, even if such investment improves the probability of winning in a conflict with the aggressor. This is because the investment in military capacity acts as a source of information for the aggressor about the reliability of the alliance between the weaker target and its stronger ally. If the weaker country invests a lot of resources into a militarization effort, the aggressor might infer that this choice is dictated by the unwillingness of the strong ally to come to the rescue of the weak target, thus making deterrence fail. We analyze two strategically different, and substantively important scenarios: one where the weaker state’s investment in military capacity and support from the stronger ally are complements, and one in which they are substitutes. In each scenario, we study the extent to which an ambiguous alliance can deter attacks, and the optimal choice of investment in military capacity for the weaker state.

Authors

• Livio Di Lonardo, Bocconi University

• Bradley C Smith, Vanderbilt University