How do the weak defeat the strong? Ivan Arreguín-Toft argues that, although many factors affect asymmetric conflict outcomes (for example, the relative power of the actors, their weapons technology, and outside support), the interaction of each actor's strategy is the best explanation. Supporting his argument with combined statistical and comparative case study analysis, Arreguín-Toft's strategic interaction theory has implications not only for international relations theorists, but for policy makers grappling with interstate and civil wars, as well as terrorism.