During World War II, Nazi Germany engaged in deliberately genocidal policies towards Soviet Union prisoners of war (POWs). This resulted in some 3.3 to 3.5 million deaths, about 60% of all Soviet POWs.
The occupation of Poland by Nazi Germany and the Soviet Union during the Second World War (1939–1945) began with invasion of Poland in September 1939, and formally concluded with the defeat of Nazism by the Four Powers in May 1945.