This book identifies contemporary military coalition defections, builds a theoretical framework for understanding why coalition defection occurs and assesses its utility for both the scholarly and policy practitioner communities. Drawing upon the author’s own experiences managing the Afghanistan coalition for the Pentagon, the volume builds a relevant policy and practical understanding of some of the key aspects of contemporary coalition warfare. Ultimately, it concludes that coalition defection is prompted by heightened perceptions of political and military risk.  Yet the choice of how to defect— whether to completely withdraw forces or instead find another, less risky way to participate—is largely a function of international and alliance pressures to remain engaged.