The history of Poland from 1939 to 1945 encompasses primarily the period from the invasion of Poland by Nazi Germany and the Soviet Union to the end of World War II. 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, the entirety of Poland was occupied by Germany, which proceeded to advance its racial and genocidal policies across Poland. Under the two occupations, Polish citizens suffered enormous human and material losses. According to the Institute of National Remembrance estimates, about 5.6 million Polish citizens died as a result of the German occupation and about 150,000 died as a result of the Soviet occupation. The Jews were singled out by the Germans for a quick and total annihilation and about 90 percent of Polish Jews (close to three million people) were murdered as part of the Holocaust. Jews, Poles, Romani people and prisoners of many other ethnicities were killed "en masse" at Nazi extermination camps, such as Auschwitz, Treblinka and Sobibór. Ethnic Poles were subjected to both Nazi German and Soviet persecution. The Germans killed an estimated two million ethnic Poles. They had future plans to turn the remaining majority of Poles into slave labor and annihilate those perceived as "undesirable" as part of the wider "Generalplan Ost". Ethnic cleansing and massacres of Poles and to a lesser extent Ukrainians were perpetrated in western Ukraine (prewar Polish Kresy) from 1943. The Poles were murdered by Ukrainian nationalists.