The Soviet invasion of Poland began when the Red Army crossed the eastern border of Poland while the country was already being overrun by Germany from the west. It was carried out under the secret protocol of the Molotov-Ribbentrop Pact, signed the previous month, which divided Eastern Europe into German and Soviet spheres of influence. Moscow justified it as protecting Ukrainians and Belarusians living in Poland, whereas the Polish government, which had been forced to flee, ordered its forces not to fight a war on two fronts. The USSR annexed the eastern territories, which were then incorporated into the Ukrainian and Belarusian republics. Tens of thousands of Polish officers and officials were later murdered, notably in the Katyn massacre of 1940, and many civilians were deported to Siberia.
Before and after
- from 3 September 1939 to 10 April 1940Phoney War
- from 4 September 1939 to 8 May 1945Defence of the Reich
- from 7 September 1939 to 16 September 1939Saar Offensive
- from 8 September 1939 to 28 September 1939Siege of Warsaw
- from 17 September 1939 to 6 October 1939Soviet invasion of Poland
- from 17 September 1939 to 6 October 1939Battle of Changsha
- 23 September 1939Death of Sigmund Freud
- from October 1939 to April 1940Nisko Plan
- 15 October 1939Construction of LaGuardia Airport
More in Wars, politics & history
- from 28 July 1914 to 11 November 1918World War I
- 28 June 1919Treaty of Versailles
- 4 June 1920Treaty of Trianon
- from 1933 to 1945The Holocaust
- 30 January 1933Hitler becomes Chancellor of Germany
- from 1 September 1939 to 2 September 1945World War II
The era
This moment belongs to the Modern era (1914 CE to 1945 CE), world wars and a changing world. You can also browse everything in the 20th century.