A force attacking a well prepared defensive one would need to outnumber them 10:1. They must have a blue-water navy capable of transporting it, the landing craft needed to get it onto the beach AND the long range aircraft to give it air-cover.
Capturing Darwin, while disappointing for the locals, is not the same as "defeating Australia". It is for good reason our fighter squadrons keep their main facilities in the south but a permanent detachment in the north.
We don't need to "out gun" Indo, merely have an effective defensive force which SHOULD include a submarine permanently on station. You don't need to sink too many troop ships to break their will. Ref Coral Sea Battle. As I recall we didn't sink any troop ships, just their defensive capacity.
We should NOT be cutting back on defence as is happening now.
