Operation Barbarossa (Unternehmen Barbarossa) was the German codename for Nazi Germany's invasion of the Soviet Union during World War II, which began on June 22, 1941.
It was a turning point for the fate of Adolf Hitler's Third Reich, in which the failure of Operation Barbarossa resulted in the final overall defeat of Nazi Germany.
The Eastern Front, which was opened by Operation Barbarossa, would become the largest theater of war in World War II, with some of the biggest and most brutal fighting, horrific loss of life, and pitiable conditions for Russians and Germans alike.
In August 1939, as Europe headed for another world war, Germany and the Soviet Union signed a non-aggression pact. Given the ideological differences between the two countries, the Nazi-Soviet pact came as a complete surprise to the other countries.