15 May
1525
- Peasant forces led by Anabaptist and proto-Communist Thomas Müntzer are defeated at the Battle of Frankenhausen. Müntzer is captured and the Peasant War in Germany ends.
1902
- Soviet pilot and recipient of the Hero of the Soviet Union Sigizmund Levanevsky is born.
1918
- The Finnish Civil War ends.
1919
- The Winnipeg general strike, organized by the Winnipeg Trades and Labour Council begins.
1921
- Basque nationalist and Autonomist activist, and translator Federico Krutwig is born.