text: Operation Barbarossa ( German : Unternehmen Barbarossa , for Frederick I ) was the code name for Germany 's invasion of the Soviet Union during World War II that began on 22 June 1941 .
simplified: Operation Barbarossa ( , named after Federick I ) was the code name for the European Axis 's invasion of the Soviet Union during World War II which began on 22 June 1941 .