September 17, 1939
Soviet Invasion of Poland
On September 17, 1939, the Soviet Union, breaking existing international treaties, launched a military invasion of Poland. The attack was the implementation of the secret protocol of the Ribbentrop-Molotov Pact and occurred when Poland was fighting a desperate battle against Nazi Germany. About 600,000 Red Army soldiers, supported by 4,700 tanks and 3,300 aircraft, crossed Poland's eastern border, beginning a period of Soviet occupation and mass repression against civilians.
