Shielding the State, Shaking the Regime: Military Alliances, Domestic Deterrence, and Internal Conflict

Why do some states experience instability in certain domains of domestic security—such as coups—but not in others, including civil wars and terrorism? This dissertation addresses this puzzle by examining the domestic role of military alliances. Although military alliances are widely understood by scholars and practitioners as instruments of international security, their potential to reshape the internal political landscapes of member states has received limited systematic attention. I argue that alliances alter the balance of power between governments and domestic challengers—rebels, coup plotters, and terrorist groups—through two primary mechanisms: signaling and capacity building. Crucially, these domestic effects are not uniform. Instead, they vary systematically with the content of alliance obligations imposed on member states and across different forms of domestic insecurity, including civil wars, coups, and terrorism. The statistical results indicate that defense pacts—alliances obligating members to defend one another—deter irregular civil wars by signaling credible external support to incumbent governments and by increasing governments’ military capacities, thereby discouraging rebellion. At the same time, however, defense pacts increase the risk of coups. This paradox stems from ambiguity over who within the regime can credibly claim allied backing, which emboldens both incumbents and rival elites. Defense pacts also deter domestic terrorism, but not transnational terrorism. Consultation pacts—alliances obligating members to consult over security concerns—are associated with lower levels of both domestic and transnational terrorism, likely because these two pacts facilitate coordination and information sharing to address lower-intensity security threats. Nonaggression and neutrality pacts, by contrast, exhibit no systematic effects on any domain of domestic security. Through the dissertation, I find the conditions under which international security commitments not only deter or provoke adversaries abroad but also recalibrate the incentives and strategies of actors at home—the central government, rival elites, and non-state challengers alike, and advance both alliance theory and the study of domestic conflict, showing why and how international commitments extend their shadow inward to reshape the prospects for peace and instability at home.