Originally Posted by TheSquealer

They had a lot of help

- Hitler misjudging how easy it would be to take stalingrad.
- Hitler misjudging how hard it would be to fight through a Russian winter (much less, several).
- Hitler misjudging Stalins resolve to keep putting young, unarmed boys in front of German machine gun bullets until Germany finally ran out of bullets.

Russias greatest feat was the speed with which they modernized their military, weapons and tactics and fought back. Making the jump from cavalry to eventually fairly well designed fighter plans and tanks. Of course, he had a tendency to murder all his ranking military offices at the slightest hint of bad news, which just caused mounting deaths and failed offensives and counter offensives.

Generally speaking, they won the war because of harsh winters and by Stalin not giving a fuck how many Russian soldiers died and by not caring what the cost was and by orchestrating the death of upwards of 30,000,000 of their own people in the process of "defending the motherland". And Stalin didn't do it alone. Germany was fighting on multiple fronts and fucked himself. Had he concentrated the full weight of Germany's military might on the Soviet Union, he would have wiped that place off the map quickly.