[Homer_J_Simpson]

William L. Shirer, The Rise and Fall of the Third Reich

[Homer_J_Simpson]

Winston S. Churchill, The Grand Alliance

[Sherman Logan]

The Japanese had also got themselves thoroughly clobbered a couple of years before by the Red Army in “border incidents” that were actually major battles.

http://en.wikipedia.org/wiki/Battles_of_Khalkhin_Gol

They were understandably not anxious to stick their hand back into that particular shredder.

That said, a Japanese attack on Siberia might have caused the Axis to win the war.