Its been said Hitler was the most valuable general the Allies had - and the irony is well pointed.
A sidebar re the 1941 Russo-Japanese non-aggression pact: a major component of the Soviet force employed in the Stalingrad encirclement were Asiatic divisions, largely Siberian, fresh, well equipped, full-strength divisions freed by the pact from the necessity of garrisoning the Northern and Eastern Soviet frontiers.
and the best soviet friend was japan, with koneje and tojo. but at the end, soviet atack japan.