With a PoD no earlier than June 22, 1941 (the first day of Operation Barbarossa), and discounting Nazi victory scenarios, what would be the minimal area of Europe controlled by the Soviets post-war?
As a starting point, a more successful Case Blue could cut off the Caucasus oil fields and severely limit the Soviet's ability to press a counterattack, buying more time for the WAllies to invade from France/Italy.