The Soviets had plenty of troops in the far east to hold the Japanese. Even if the japanese would prepare a decent sized army for it. The Japanese could march, the Soviet retreat untill the supplylines of the japanese dry out and they come to a halt. They would have gained nothing, not unless they pass Mongolia which is further than Berlin to Moscow.
not it didn't. the Arctic route remians open so supplies will still flow.You mean advance in the east?
Yes, it would have cut off the port where 50% of Lend-Lease came in. The least dangerous route too.