This book explores underexamined sites of interactions and encounters between humanitarians and medical workers during the long Second World War (1931-1953).It traces circulations of humanitarian actors, knowledge, and practices across the world from a conflict to another. In doing so, it demonstrates that the conflict brought about unlikely aid coalitions and intimate networks of aid, and led to a transformation of the relationships between some European organisations and colonial 'peripheries', leading to the emergence of new activities and actors. This book also interrogates the traditional dichotomy between civilian and military cultures of rehabilitation, and readdresses the role of the United States and its rise as a 'humanitarian superpower'.