Operation Barbarossa was Adolf Hitler's surprise attack on the Soviet Union in the summer of 1941. The attack was a "surprise" because Hitler and the Soviet leader, Josef Stalin, had cooperated previously on several ventures.

Operation Barbarossa was the codename for Nazi Germany's invasion of the Soviet Union during World War II that commenced on June 22, 1941. The operation was named after the Emperor Frederick Barbarossa of the Holy Roman Empire, a leader of crusades in the 12th century: according to Nazi ideology the conquest of 'inferior races' was similarly righteous. It is not to be confused with the whole war on the Eastern Front.