The Soviets and the Nazis were allied together until just before the German Invasion. A few weeks before, Germany started making the same rumblings they had about Poland about Soviet aggression and troop buildups. Stalin should have seen the hand-writing on the wall. US Communists and Nazis were allied together in the Isolation movement. The Commies did an about face after the Invasion, losing many of their pacifist followers. The Nazis were rounded up.
I am listening to radio reports from Dec 7-8, 1941. It's interesting to hear the rumors of the times. There is some speculation that Germany had bombed Pearl Harbor. Japs using Stukas in a suicide raid on Pearl Harbor. A Jap carrier being sunk. The Bismark spotted in the China Sea. Calls for a blockade of Japan.