Heroes, Traitors, and Survivors in the Imperial Borderlands redefines Southeastern Europe’s role in modern military history. Long dismissed as a “powder keg” of violence, the region emerges here as a crucial laboratory of military innovation, governance, and state formation in the early 20th century. Spanning the Ottoman Empire, Habsburg Monarchy, Montenegro, Serbia, and the Kingdom of Serbs, Croats, and Slovenes, the book traces how mobilization operated as a negotiated process between state elites, military brokers, and local communities rather than as a purely coercive act. Using a transimperial and multiscalar approach, this book examines how small states mobilized vast armies with unprecedented speed, thereby often outpacing larger empires and balancing between acceptance, endurance, and refusal while employing pragmatic tools such as land reform, tax relief, and social welfare to secure participation. By repositioning Southeastern Europe as a laboratory of military mobilizations, Heroes, Traitors, and Survivors in the Imperial Borderlands highlights the overlooked roles of women, non-combatants, and military entrepreneurs in shaping wartime and post-war societies. Richly grounded in multilingual archival research, it offers a new lens on the relationship between empire, nation, and militarization, appealing to scholars and advanced students of European, military, and (trans)imperial history, as well as general readers interested in the global dimensions of modern warfare.