Read some history yourself. When the Eastern front broke the Germans were gaining ground daily. The Russian Army melted away. The only thing stopping them at that point was how far they could walk and how fast. All that saved Russia was the fact that the Germans wanted to tranfer troops West to try and defeat the Allies.
Gaining ground at the rate of several kilometers daily, well that's only about 800 kilometers to Moscow, sure, pack your bags now. Besides, the capital was in Saint Petersburge, but we'll ignore that fact too.