An open access title available under the terms of a CC BY-NC-SA 3.0 IGO licence. It is free to read at Oxford Academic and offered as a free PDF download from OUP and selected open access locations. This book explores the emergence of wartime governance and its enduring effects on post-conflict state-building, development, and institutional change. Drawing on rich empirical research and original case studies from conflict-affected countries across Africa, Latin America, and Asia, it brings together leading scholars in political science, development studies, and economics to examine how non-state and hybrid actors govern during war, and how these forms of governance interact with, challenge, or complement state authority in the long term. Rather than portraying war solely as a period of state collapse and institutional erosion, this volume reveals the emergence of complex systems of rule that provide public goods, administer justice, and collect revenues. These wartime institutions often reshape postwar political settlements, influencing patterns of state legitimacy, social cohesion, and local development trajectories. By bridging disciplinary boundaries and combining theoretical innovation with grounded fieldwork, the book sheds light on key policy debates about peacebuilding, humanitarian interventions, and institutional reform in fragile contexts. It argues for a nuanced understanding of wartime governance - not merely as a symptom of conflict but as a central force in the political and institutional evolution of societies affected by war. This volume is essential reading for scholars, policy-makers, and practitioners seeking to understand the dynamics of authority, legitimacy, and governance in the world's most challenging settings.