The role of religion in war and post-war times has regained central importance in public discourse, particularly in Western countries. After decades of research on religion and peace – and especially Christianity and peace – public and academic attention has (re)turned to war and violence in the history of religions in general and of Christianity in particular. This collection brings together scholars from theology, history, area and cultural studies to examine the relationships between wars and Christian internationalism in the late nineteenth and early twentieth centuries. The contributions cover case studies from China, France, Germany, India, Japan, Korea, the Middle East, North America, Scandinavia and Southern Africa. The temporal range goes beyond the narrow focus of the First World War and includes wars between non-Western countries and colonial wars. Many chapters open the topic up to non-Western perspectives and enlarge our understanding of the role of the young ecumenical movement in war and post-war times and, beyond that, they demonstrate how in the wars of a century ago Christians tried to negotiate between internationalist and nationalist views and to deal with and overcome wartime disruptions. https://creativecommons.org/licenses/by/4.0/