[Russia lost 27 million people in the war ( at least 10 million military) and killed over a million nazis on the Eastern Front.
Had it not been for Russia fighting against a German war of extermination, pulling the nazis into the interior of Russia and defeating them at the cost of millions killed by war and starvation]
As you quite aptly pointed out, the Russians had no choice. They could fight or literally be killed to the last man, woman and child. The Russians were a pack of wolves who fought not because they were looking to save the world, but because they did a deal with the Nazis, the other pack of wolves. Heck, the Nazis did not even really double-cross the Soviets. The Soviets had a plan to attack the Nazis once they were suitably softened up in their war with the French and the British. Stalin did not expect the Nazis to enjoy a quick victory in the West. That’s why the Soviet plan to attack Germany first never got off the ground - Stalin thought the Germans were still too strong to double-cross.
https://en.wikipedia.org/wiki/Soviet_offensive_plans_controversy
You are absolutely correct in the first half of your statement. I haven’t ever heard the second half (Stalin had a plan to attack the Germans after they were softened up), but given his nature, I have no doubt that it’s correct, whether documented or not (haven’t looked at your link yet). Good post.