Forthcoming, Journal of Conflict Resolution. In contrast with previous research that has focused on the ability of sanctions to send credible signals or impose costs, in this paper we argue that states often use sanctions to destroy their adversaries’ military capabilities. In particular, we show that sanctions can be used to smooth shifts in the balance of power that would otherwise lead to preventive war. After presenting a game-theoretic model of shifting power and sanctions, we discuss several cases in which sanctions were explicitly imposed to destroy an adversary’s military capability in expectation of a shift in the balance of power. We also explore the implications of this argument for the evaluation of sanctions’ effectiveness. Because sanctions may be deployed as a mechanism to lock in the status quo rather than revise it, the outcome of a sanctions episode must be compared to its counterfactual — i.e., a world in which sanctions were not imposed — rather than the status quo ante. Our argument suggests that sanctions may be effectively deployed in response to expected adverse shifts in the balance of power; therefore observed outcomes disadvantageous to the sanctioning state are insufficient proof that sanctions have failed.