The only thing I'd add to this article and the comments is: the Germans failed to realize that when they'd gone hundreds of miles into Russia over bad roads, with hostiles in their rear, they'd have a real serious problem supplying all those troops. The Russians call those "generals" of theirs General Distance (along with General Mud and General Winter).
We can't separate the problems any Russian invader would have from the tenacious resistance to this invasion. They were both essential. As was all the American help; particularly the trucks.
> American view that the Soviets were useless and won just because of large numbers, General Winter and of course American help.
I think even harder to swallow is that Soviet technology was at least equal to US weapons. Their tanks are well known as being great, but their fighter planes were (especially the Yak-3, Yak-9 and La-7) were at least as good as comparable US and British planes.
Quote from article: Overall, by 1944 the Axis could deploy only a small fraction of their potential military capacity into combat—it was being destroyed in a multi-layered campaign long before it could be used against their enemies. This was the true battlefield of WWII, a massive air-sea super battlefield that stretched for thousands of miles not only of traditional front but of depth and height