OTL, the Australian government asked the UK to return troops home (from North Africa?-can't recall offhand) to shore up against increased Japanese threats. But what if either the need in Europe/UK was too great or the transportation was not available and Australia had to make do without them? Not so much the political fallout, but simply the military. Since Japan never attacked, probably nothing different would have resulted. But would there be any significant changes in troop dispositions and other defensive preparations?