Deterrence with a Self-Enforcing Threat

Abstract

A central puzzle in the study of deterrence is how threats can be credible when they are meant to defend interests that do not immediately appear to be worth fighting over. We develop a formal model in which a defender fears a challenger’s potential future belligerence, and seeks to deter her from attempting a transgression that yields both direct and military benefits. We identify conditions under which responding with war is a credible deterrent threat even when both the magnitude of the transgression and the defender’s level of fear are objectively small. In the equilibrium, the defender is able to infer the challenger’s future belligerence from her very willingness to transgress in the face of a credible threat, and is therefore willing to carry out that threat because he prefers war sooner to war later. The challenger is consequently deterred unless she prefers immediate conflict, fulfilling the defender’s expectations. We also show that the difference between the military and direct value of a transgression plays a crucial role in determining the effectiveness of deterrence, and that introducing fear about a challenger’s intentions can strengthen deterrent threats. We demonstrate the robustness of our results to a variety of extensions, and apply the model to analyze the Turkish Straits Crisis of 1946.