Byline: David B. Carter This article introduces the idea of a compellence dilemma. This dilemma arises when the domestic policies of adversaries-such as hosting violent groups-threaten states' security. Such states often consider coercive instruments to compel their adversary to change those policies. The problem? The prospect of costly punishment makes cooperation more attractive for the adversary. However, if they fail to coerce policy change, harsh punishments can reduce the adversary's capacity to enact policy change and induce harmful domestic instability. These problems are compounded by the fact that both the threatened states' incentive to use costly punishments and the costs of failed compellence increase with the severity of the security threat. The logic of the compellence dilemma applies whenever a state uses damaging coercive instruments but risks failing to achieve its immediate objectives. I analyze the compellence dilemma with a dynamic game-theoretic model of interaction among a target state, host state, and violent group, and show that it is pervasive in equilibrium. I show that the compellence dilemma causes states to refrain from using harsh punishments even when they would compel the host state to cooperate. Concerns about decreasing future host-state capacity and increasing group power drive this result. Article Note: Authors's note: Thanks go to Deniz Aksoy, Michelle Benson, Robert Braithewaite, Steve Brams, Jon Caverley, Bridget Coggins, Mark Fey, Hein Goemans, Joanne Gowa, Tasos Kalandrakis, Matt Lenoe, Vipin Narang, Dan Nexon, Kris Ramsay, Ken Schultz, Idean Salehyan, Curt Signorino, Jake Shapiro, Randy Stone, and two anonymous reviewers for comments on this project. Any mistakes remain my own responsibility. CAPTION(S): Appendix S1. The Compellence Dilemma: Supplementary Appendix.