The Eastern Front of World War II was a theatre of conflict between the European Axis powers and co-belligerent Finland against the Soviet Union (USSR), Poland and other Allies, which encompassed Central Europe, Eastern Europe, Northeast Europe (Baltics), and Southeast Europe (Balkans) from 22 June 1941 to 9 May 1945. It was known as the Great Patriotic War in the Soviet Union and some of its successor states, while everywhere else it was called the Eastern Front.
https://en.wikipedia.org/wiki/Eastern_Front_(World_War_II)