WHAT ALL HAPPENED JUNE TO OCTOBER 1939
Find out what all happened June to October 1939

World War II: The Battle of Hel begins, the longest-defended pocket of Polish Army resistance during the German invasion of Poland. (9. September 1939)

Warsaw surrenders to Nazi Germany during World War II. (28. September 1939)

General George C. Marshall becomes Chief of Staff of the United States Army. (1. September 1939)

Last public guillotining in France: Eugen Weidmann, a convicted murderer, is guillotined in Versailles outside the Saint-Pierre prison (17. June 1939)

The Baseball Hall of Fame opens in Cooperstown, New York. (12. June 1939)

World War II: Polish government of Ignacy Mościcki flees to Romania. (18. September 1939)

The Wound Badge for Wehrmacht, SS, Kriegsmarine, and Luftwaffe soldiers is instituted. The final version of the Iron Cross is also instituted on this date. (1. September 1939)

World War II: Nazi Germany and Slovakia invade Poland, beginning the European phase of World War II. (1. September 1939)

World War II: The Estonian military boards the Polish submarine ORP Orzeł in Tallinn, sparking a diplomatic incident that the Soviet Union will later use to justify the annexation of Estonia. (14. September 1939)

Albert Einstein and Leó Szilárd write a letter to Franklin D. Roosevelt, urging him to begin the Manhattan Project to develop a nuclear weapon. (2. August 1939)

World War II: Canada declares war on Nazi Germany, joining the Allies – France, the United Kingdom, New Zealand and Australia. (10. September 1939)

First flight of the German Focke-Wulf Fw 190 fighter-bomber airplane. (1. June 1939)

Romanian Prime Minister Armand Călinescu is assassinated by far-right legionnaires of the fascist paramilitary organization called the Iron Guard. (21. September 1939)

Siam is renamed Thailand by Plaek Pibulsonggram, the country's third prime minister. (24. June 1939)

Holocaust: the last remaining Jewish enterprises in Germany are closed. (6. July 1939)

World War II: Germany annexes Western Poland. (8. October 1939)

Switzerland mobilizes its forces and the Swiss Parliament elects Henri Guisan to head the Swiss Army (an event that can happen only during war or mobilization). (1. September 1939)

General Władysław Sikorski becomes commander-in-chief of the Polish Government in exile. (30. September 1939)

Holocaust: The MS St. Louis, a ship carrying 963 Jewish refugees, is denied permission to land in Florida, in the United States, after already being turned away from Cuba. Forced to return to Europe, more than 200 of its passengers later die in Nazi concentration camps. (4. June 1939)

The United Kingdom and Poland form a military alliance in which the UK promises to defend Poland in case of invasion by a foreign power. (25. August 1939)