Nice game I have had a more then few games like these myself. 9-1-1 with 3 on going. Most of the 9 resign long before winter.
The general story goes like this as it appears yours has:
Generally the russian player has played several newbie Germans holding them at rivers and crushing them come Blizzard. So they think they have mastered the game and are way over confident in there overwhelming skills. They have no clue they have been playing newbies. They have no idea there all forward tactics are a dream come true for a experianced German player.
You push to Leningrad in 4 or 5 turns and or over the Dnepr on turn 5 and they basicly panick and its just a joy after that as the German
Always nice when I am looking for an opponent and get a reply back "I have played some games and all my enemys resigned before 42. I wish I could get a German that will stick it out until 42."

you've got a winner!
Logistics are the key.
Nice job humbling your "uber" opponent.
Pelton