>>509883381As I stated before, even if Japan had been completely unopposed in a landing, they never would have occupied australia unless the sino japanese war had ended. To much drain, too few resources discovered in that time period.
Same issue with Karafuto in the north. Noone knew at the time it had some of the most valuable energy deposits in the world, so japan gave it up to russia without much of a fight.
If they had known, Japan probably would have evacuated all of korea, manchuria, and china to stop the russians from taking an inch.