**Edit; I forgot to say, take this in addition to what everyone else said.

Before we talk about the great patriotic war, let’s mention the Soviet-Finnish War (Winter War). The TLDR version of the war is, essentially, the Soviets had a bunch of military leaders who obtained their ranks during the civil war (also known as the revolutionary war) essentially by switching sides. And as it turns out, some of them were incompetent and couldn’t design a simple battle plan to fight Finland. After an investigation, it was found that the military leadership was also filled with opportunists who may not have believed in Marxism, and thus the purge happened.

The Red Army’s remaining leadership ranged from good enough but untested to flat-out incompetent. Not a lot of the Red Army’s leadership had been given a baptism by fire, simply because much of the portion of it that had been needed to be removed from power. Hitler had a good position laid in front of him, all he had to do was reach Moscow before the Soviets could raise better leaders. Thankfully the winters halted the front, which bought the Soviets time and they were able to find solid leadership to push the Germans back.

The reason Hitler made it so deep into Soviet territory was twofold.

• Lacking military leadership, the Soviets were too weak to hold against the Germans; and

• Until the Americans got involved in the war, Germany could focus its efforts on the eastern front. But once the Americans took Rome Germany’s forces spread thinner, and once the Americans landed in Normandy Germany spread itself too thin.

To that point, a part of what tore Hitler down (and is something that’s worth looking at to better understand the psychology of fascism) was his ambition and his inability to estimate the strength of his forces. If Hitler didn’t antagonize the US he may have done better in the war. But there’s no reality where Hitler wins, mind you. The war was all around unwinnable. Even if the Americans didn’t get involved in the war, the Soviets were still eventually going to take Berlin. And if they had to, they would’ve kept pushing to Italy and France to end the Fascist scourge.