History of Poland (1939–1945)

The history of Poland from 1939 to 1945 encompasses primarily the period from the Invasion of Poland by Nazi Germany to the end of World War II. The outbreak of the war followed the period of intense armament by Nazi Germany and other neighbors of Poland, with which Poland was unable to keep up because of the country's limited economic resources.

Following the German-Soviet non-aggression pact, Poland was invaded by Nazi Germany on 1 September 1939 and by the Soviet Union on 17 September. The campaigns ended in early October with Germany and the Soviet Union dividing and annexing the whole of Poland. After the Axis attack on the Soviet Union in the summer of 1941, all of Poland was occupied by Germany.

Under the two occupations, Polish citizens suffered enormous human and material losses. It is estimated that about 5.7 million Polish citizens died as a result of the German occupation and about 150,000 Polish citizens died as a result of the Soviet occupation. Ethnic Poles were subjected to both the Nazi and Soviet persecution. The Jews were singled out by the Germans for a quick and total annihilation and about 90% of Polish Jews (close to three million people) were murdered. Jews and others were killed en masse at Nazi extermination camps, such as Auschwitz, Treblinka and Sobibór. Ethnic cleansing and massacres of civilian populations, mostly Poles, were perpetrated in western Ukraine from 1943. The historically unprecedented war crimes committed in Poland were divided at the postwar Nuremberg trials into three main categories of wartime criminality: waging a war of aggression, war crimes, and crimes against humanity.

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