Over the last ten years, the study of foreign volunteering has been enriched by novel interpretations of the past alongside new insights drawn from the large cohorts of foreign fighters in the conflict in Syria and, more recently, in Ukraine. Researchers have introduced new sources and ideas in studying the International Brigades of the Spanish Civil War. At the same time, historians and political scientists have begun to compare cases of foreign volunteering across several conflicts in an attempt to identify commonalities and differences. This introductory chapter surveys the recent literature, focusing on studies that seek to define and demarcate foreign volunteering, to understand the motivations that prompt individuals to go abroad to fight, and to examine their wartime experiences, postwar trajectories, and how they are remembered.