Alliance Dynamics in the Shadow of Shifting Power

Abstract

Abstract Alliances are costly to form and to terminate, and yet alliances change frequently. Scholars typically attribute these decisions to static factors, such as the power balance, and retrospective ones, such as past power shifts. We highlight another factor: prospective changes, particularly anticipated military strength shifts. We analyze a three-country bargaining model of alliances and war that incorporates forward-looking power dynamics. The model, unlike those restricting players to set roles, flexibly allows players to ally in any arrangement. We find that alliance arrangements that are optimal when power is static are often suboptimal when power fluctuates. Maintaining prior alliances despite expected power shifts may even lead to preventive war. States thus strategically look to the future to identify optimal alliances in the present. Quantitative analyses corroborate the expectation. As the anticipated size of power shifts increases, alliance changes become more common. Accordingly, states navigate expected changes in the international landscape by rearranging current alliance commitments that can help minimize the risk of conflict. When power balances are in flux, malleable institutional arrangements may prove preferable to rigid ones.