This book explores the military and economic contributions of European reservists in Argentina and Argentine-born volunteers to the First World War. Drawing on primary sources in five languages, it explores all stages of the military mobilisation process—the recruitment and selection of reservists and volunteers, their transfer to the war theatre, training and assignment to units, diverse wartime and combat experiences, demobilisation, return to Argentina, and reintegration into civilian life. Additionally, it examines the economic mobilisation of these communities in support of the war effort, the variations in their responses to recruitment, and, in the aftermath of the war, the commemoration of their human and material contributions. Part of the Wars and Battles of the World series, this book will be an essential read for scholars and researchers of military history, migration studies, nationalism studies, global and transnational history, First World War studies, and Argentine and Latin American history.