A coordiated "invasion" would be out of the question the logistics would be almost impossible even with Aluetions occupied the japs couln't sta supplied over that great of distance. Mabye if they discovered oil first.The germans had it worse.No real surface fleet to speak of for support they had to occupy Iceland then Greenland.I don't think they could mount somthing that big.Small raids on big targes only if ultra didn't play its part.