
A full scale invasion was off the plan for the Japanese. Oz was too big and would stretch their resources too much, and a lot of resources were still to be discovered, so no great returns to be had. The raid scenarios, or a temporary lodgement for disruption and PR purposes, however, were possibilities that would yield a few good games. The NorForce and Pilbara Regiment boys insist that Japanese did make landings on the north coast during WWII, in small parties (scouts or air raid related?) which avoided contact and didn't stay long.
ET, if you ever get down to the 'gong then the Breakwater Battery Museum at Kembla is pretty good- when it's open. The 6" gun pits are still there, though the dragon's teeth are probably post WWII- and wouldn't have been painted gloss white.