WHAT ALL HAPPENED SEPTEMBER TO OCTOBER 1939
Find out what all happened September to October 1939

World War II: France, the United Kingdom, New Zealand and Australia declare war on Germany after the invasion of Poland, forming the Allies. (3. September 1939)

World War II: South Africa declares war on Germany. (6. September 1939)

World War II: A German U-boat U 29 sinks the British aircraft carrier HMS Courageous. (17. September 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)

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)

After a one-month Siege of Warsaw, hostile Nazi forces enter the city. (1. October 1939)

World War II: Germany's invasion of Poland ends with the surrender of Polesia army after the Battle of Kock (6. October 1939)

Pope Pius XII publishes his first major encyclical entitled Summi Pontificatus. (20. October 1939)

The German submarine U-47 sinks the British battleship HMS Royal Oak within her harbour at Scapa Flow, Scotland. (14. October 1939)

World War II: The Battle of Kępa Oksywska concludes, with Polish losses reaching roughly 14% of all the forces engaged. (19. September 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)

Joint victory parade of Wehrmacht and Red Army in Brest-Litovsk at the end of the Invasion of Poland. (22. September 1939)

Nazi Germany and the Soviet Union agree on a division of Poland after their invasion during World War II. (28. September 1939)

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

Burmese national hero U Ottama dies in prison after a hunger strike to protest Britain's colonial government. (9. September 1939)

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

World War II: The submarine HMS Oxley is mistakenly sunk by the submarine HMS Triton near Norway and becomes the Royal Navy's first loss. (10. September 1939)

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

The Japanese Mitsubishi G4M twin-engine "Betty" Bomber makes its maiden flight. (23. October 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)