Hitler fired key generals in the midst of it.
But you claimed these generals were incompenent! :)
Germans took too much land too quickly and let supply lines stretch..
They had to, given how many troops were behind Stalins line and how significant were the 3 main cities they attacked.
Uhhh.. The Russians barely escaped the Finns
Last i checked they overrun Finnland, eventually. Not to mention they had to contend with Mannerheims line and winter.
Now go read up, its fun reading history American style though:)