Instability, Intervention, and Inter-Power Politics

Domestic political and economic instability provides a window of opportunity for external military intervention. To examine the factors that underlie the strategic decisions to pursue military intervention in the presence of instability, I develop a game-theoretic model in which two external powers sequentially decide whether to intervene militarily in a third country. The level of domestic instability in the target country is modelled as a stochastic random walk process. In the model, powers with conflicting policy preferences have incentives to intervene preemptively in order to eliminate the possibility of future interventions by a rival power. Given this, I argue that major powers are most likely to intervene in their spheres of influence when there exists an external threat of intervention by another power. I support this claimwith an historical analysis of the variation in U.S. intervention activities in the Caribbean Basin over time. ∗The author would like to thank Sarah Croco, Paul Huth, Jim Morrow, Robert Walker, and the participants at the 2003 Empirical Implications of Theoretical Models Summer Institute at Ann Arbor, Michigan, for helpful comments on previous versions of the paper.