Question

Why is hitler attack on the Soviet union in 1941 regarded a historic blunder

Answer 1

During 1941, Germany was already fighting the allied forces on the western front of it's empire. Attack on Russia led to fighting between the two powers on the eastern front of the German empire. In this way, It got 'cornered' from both sides which eventually led to it's downfall.

Answer 2

In June 1941, Hitler attacked the Soviet Union. The German western front was exposed to British aerial bombing and the eastern front was crushed by the powerful Soviet Red Army at Stalingrad. Thus the Soviet established its leadership over entire Eastern Europe for the next 50 years. This was the historical blunder committed by Hitler.