Designing Security: Treaty Alliances and Material Commitments

• In Event: Foreign Military Interaction

Abstract

Why do security commitments between military allies vary? Most of the literature on extended deterrence and alliances focuses on treaty commitments, or written legal agreements of defense, and their effects on the likelihood of conflict. Yet security commitments between allies are not limited to treaty alliances alone. There exists a subset of commitment mechanisms -- what I refer to as material commitments -- that remains largely unaccounted for but has significant effects on crisis bargaining behavior. Material commitments represent physical, military measures taken in peacetime that prepare allies for war, such as arms transfers, an integrated military command, overseas military bases, and joint military exercises. In this paper, I present a formal model that examines how material commitments influence the strategic environment in different ways from treaty commitments. The model outlines the conditions under which a third-party defender will choose to make certain types of security commitments to its protege over others, and why a defender would make costly ex ante commitments even if it would abandon its ally in conflict. I find that a defender is more likely to make a material commitment that improves joint war-fighting capabilities when it prefers to support its protege in conflict, but would improve the protege's unilateral capabilities when it prefers to not involve itself in war. By parsing out variations in security commitments and their different effects on the strategic environment of actors in dispute, we uncover new equilibrium behavior that current models cannot explain. The analysis of material security commitments has important theoretical and empirical implications for the design of alliances, the deterrence-restraint dilemma, and ally reliability in crises.

Author

• Stephanie Kang, University of Southern California