In the first independent study of the League of Red Cross Societies, an interdisciplinary team of leading scholars examine its history, and how it influenced twentieth-century humanitarianism. They explore how the League evolved from 1919 to 1991 as a peacetime organisation of the Red Cross in contrast to the original wartime focus of the International Committee of the Red Cross. Investigating largely unknown, but significant actors, they shed new light on the League's activities in Southeast Asia, the Horn of Africa, Latin America and Europe through case studies focussing on its global health initiatives, the complexity of its networks in war and peace, and its role in providing relief. The authors argue that it is impossible to understand today's Red Cross and Red Crescent movement and global humanitarianism without considering the structures, expertise and training provided by the League to member National Societies from 1919 to 1991.