Why are allies so unpredictable? In American Allies in Times of War, Stéfanie von Hlatky tackles this question by examining military cooperation between the United States and its allies. First, this book demonstrates that alliance demands in times of war cannot always be met by democratic allies due to domestic political constraints. Second, concerns over the delivery of military assets can further curtail the ability of governments to commit resources to war. The author convincingly argues that it is essential to account for these factors to understand the varying levels of military cooperation observed between the US and its closest partners. This book offers an original comparative analysis of the United Kingdom, Canada, and Australias response to the wars in Afghanistan and Iraq. The case studies highlight that decisions involving the use of force must address both domestic-level constraints and the importance of the bilateral relationship with the United States. This book explains how American allies can manage requests for political and military support by resorting to effective negotiation strategies to influence the terms of cooperation. American Allies in Times of War offers a comprehensive analysis of why and how allies go to war together and dispels some myths and misconceptions about the politics behind military cooperation. It is intended for policymakers, academics, and students who want to gain insight into how foreign and defence policy is made and how domestic pressures and operational constraints impact contemporary military engagements.