WHAT ALL HAPPENED MAY TO DECEMBER 1939
Find out what all happened May to December 1939

Winter War: The Soviet Union is expelled from the League of Nations for invading Finland. (14. December 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)

Judge Joseph Force Crater, known as the "Missingest Man in New York", is declared legally dead. (6. June 1939)

World War II: The United Kingdom and France begin a naval blockade of Germany that lasts until the end of the war. This also marks the beginning of the Battle of the Atlantic. (3. September 1939)

Adolf Hitler signs an order to begin the systematic euthanasia of mentally ill and disabled people. (1. September 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)

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

Shooting begins on Paramount Pictures' Dr. Cyclops, the first horror film photographed in three-strip Technicolor. (12. June 1939)

Gone with the Wind receives its premiere at Loew's Grand Theatre in Atlanta, Georgia, United States. (15. December 1939)

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

The Nazi propaganda broadcaster known as Lord Haw-Haw begins transmitting. (18. September 1939)

First flight of the turbojet-powered Heinkel He 178, the world's first jet aircraft. (27. August 1939)

World War II: The Battle of the Heligoland Bight, the first major air battle of the war, takes place. (18. December 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)

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)

Lina Medina becomes the youngest confirmed mother in medical history at the age of five. (14. May 1939)

World War II: The Battle of Barking Creek. (6. September 1939)

HMS Duchess sinks after a collision with HMS Barham off the coast of Scotland with the loss of 124 men. (12. December 1939)