I haven't checked previous posts on this, but I thought I would put it forward. Obviously, Hitler had a frothing at the mouth hatred of communists and Slavs so it was probably never going to be a runner! However Stallin did not believe the pact was broken until the Nazis were well inside Soviet territory,he was paranoid about everything it seems except bizarely that! I don't recall the opposition being as vociferous when the Stallinists invaded Finland and assisted in the invasion of Poland compared to the stern views taken of the Nazis!
Is this a scenario where the Nazis and Stallinists can prevail over all Europe?
No doubt the Stallinists could be urged to become willing accomplices in the extermination of peoples who were targetted for extermination though the communists in this instance would be mostly theTrotskyists!