Do military alliances deter or provoke conflict? This book explores this critical question by examining the often-overlooked phase of alliance implementation, a complex and prolonged process that occurs before an alliance's deterrent benefits are realized. Brett V. Benson and Bradley C. Smith argue that the formation of new alliances does not immediately translate into increased military strength. Instead, states must navigate political and military challenges to operationalize their alliance, creating a vulnerable window of time before an alliance is implemented. Benson and Smith reveal that while fully realized alliances can enhance deterrence and foster peace, their preliminary stages can provoke conflict, as potential enemies may wage preventive war to counteract the anticipated shift in power. To address these risks, The Window Before details strategies employed by allies, including crafting less provocative treaty terms, accelerating the implementation process, and maintaining secrecy to minimize adversaries' chances to react. Through in-depth theoretical analysis and historical examples, the book sheds light on the effectiveness of these strategies and their broader implications for alliance dynamics and international relations. It offers crucial insights into current global tensions, including the ongoing war in Ukraine, China-Taiwan relations, and the emerging no-limits security partnership between Russia and China. In a world undergoing epochal shifts in alliances ranging from Europe to the Middle East to East Asia, this methodologically rigorous book provides the necessary theoretical framework for understanding why alliance shifts happen and predicting the fallout--potentially devastating--that may result.