The civilian population of the territory in conflict suffered terribly from the war, in part because of the horrific occupation policies of the German (and the Soviets), and in part because of a lack of food and other necessities of life. Around 15 million Soviet civilians are thought to have been killed. Some three million ethnic Poles died (some before the German invasion of the Soviet Union, but many after) along with around three million Jews of Polish and another two million of Soviet citizenship (included in the Soviet statistics). Somewhere between 500000 and 2 million German civilians died in the expulsions that followed the war.
The war between Germany and the Soviet Union officially began in late June 1941, although the threat of conflict had loomed since the early 1930s. Germany and the USSR launched a joint war against Poland in September of 1939, which the Soviets followed up with invasions of Finland, Romania, and the Baltic states across the following year.
After Germany crushed France, and determined that it could not easily drive Great Britain from the war, the Wehrmacht turned its attention back to the East. Following the conquests of Greece and Yugolavia in the spring of 1941, Berlin prepared its most ambitious campaign; the destruction of Soviet Russia. The ensuing war would result in a staggering loss of human life, and in the final destruction of the Nazi regime.