Wouldn't such an invasion be immediately crippled by the fascists cutting off supplies at the Bering Strait? It's not like the RU would be taken by surprise with its insanely effective foreign service. Do you see the Russians trying to march an Army through this?:
Hint: Everything in that photo has water under it.
Trying to get supplies over Muskeg is only slightly more realistic than the Russians marching an army over the north pole. Maybe I don't have faith in Viktor's military but I don't see the soldier fanatics of the Republic Union having much trouble with an enemy whose supply chain stretches 2/3s around the planets northern hemisphere.