Why do some international crises between major states escalate to war while others do not? To shed light on this question, this book reviews fifteen such crises during the period 1815–present, including the Crimean War, The Franco-Prussian War, the Cuban Missile Crisis, and the 2022 Russia-Ukraine War. Each chapter places the crisis at hand in its historical context, provides a narrative of the case's events that focuses on the decision-makers involved, theoretically analyses the case's outcome in light of current research, and inductively draws some lessons from the case for both scholars and policymakers. The book concludes by exploring common patterns and drawing some broader lessons that apply to the practice of diplomacy and international relations theory. Integrating qualitative information with the rich body of quantitative research on interstate war and peace, this unique volume is a major contribution to crisis diplomacy and war studies. ‘Why some crises escalate to war while others do not is a critical question for both theorists and policymakers. Vasquez and Owsiak answer with a masterful integration of theory, data, and history in a penetrating analysis of decision-making in fifteen of the most important international crises of the last hundred years.' Jack S. Levy, Rutgers University ‘A theoretically and empirically rich examination of when and how international crises escalate to war and when they do not. This book offers fascinating materials on a wide range of cases in the modern era and the plausible explanations for their occurrence. New and old research findings on crises and war are assembled and evaluated for an easy to read, yet thorough analysis.' T. V. Paul, Distinguished James McGill Professor, Department of Political Science, McGill University and co-editor of International Organizations and Peaceful Change in World Politics (Cambridge University Press, 2025) ‘For anyone teaching classes on diplomacy, conflict, and international relations, I highly recommend this book. Vasquez and Owsiak provide a detailed historical analysis of 15 crises between 1839-2014, seven of which escalated to war. By analyzing a wide set of theoretical factors in each case, the book helps readers learn why territorial issues, domestic politics, alliances, and bargaining strategies have significantly increased the risks for crises to escalate to war. Students gain valuable historical information about each crisis and walk away with a better understanding of the causes of war more broadly.’ Sara McLaughlin Mitchell, University of Iowa ‘Combining theoretical insight, deep historical perspective, and fine-grained examination of decision-making, this book addresses one of the enduring questions of international history and pressing challenges of our day: what conditions are likely to constrain or bring about war between major powers. Historians will benefit from engaging with this invaluable analysis of two centuries of crisis diplomacy.’ William Mulligan, University College Dublin This book distinguishes crises that escalate to war from those that do not, through analysis of fifteen interstate crises (1815–present). John A. Vasquez is Professor Emeritus at the University of Illinois at Urbana-Champaign. He is the author of The War Puzzle (Cambridge, 1993), The War Puzzle Revisited (Cambridge, 2009), The Power of Power Politics (Cambridge, 1999), The Steps to War (with Paul Senese), Territory, War, and Peace (with Marie Henehan), and Contagion and War: Lessons from the First World War (Cambridge, 2018). He received the Lifetime Achievement Award from the APSA Conflict Processes Section and has served as the president of the Peace Science Society (International) and the International Studies Association. Andrew P. Owsiak is Professor of International Affairs and Josiah Meigs Distinguished Teaching Professor at the University of Georgia. His research concerns interstate conflict and its management. His recent published works include On Dangerous Ground (with Toby J. Rider, 2021), International Conflict Management (with J. Michael Greig and Paul F. Diehl, 2023), and various journal articles.