The Greco-Turkish war erupted on May 15, 1919. The war resulted in the largest compulsory population exchange in history up to that time (2 million people) and helped define the concept of ethnic conflict. The war also brought about the Turkish Republic and its severity indelibly shaped modern Greece and Turkey to this day. Written by Christopher Kinley. Narration by Dr. Nicholas B. Breyfogle. Video production by Hannah Keller, Dr. Nicholas B. Breyfogle, Justin Troyer, and Victoria Paige. A transcript is available at https://origins.osu.edu/milestones/may-2019-greco-turkish-war-smyrna-sakarya-kemal-ottoman. This is a production of Origins: Current Events in Historical Perspective at the Goldberg Center in the Department of History at The Ohio State University and the Department of History at Miami University.