Do you really think that Curtin and co. had the defense of South Australia in mind???
The Brisbane line was in name only.
You guys were as screwed as we were!
But let's take this one step further shall we...
Let's say that Indonesia invaded tomorrow.
Which state do you think that they would defend first??
You or us???
Pretty obvious isn't it.
No, the Brisbane line had Adelaide in mind.
No one cared about the Western Colony of peasants.
If Indonesia invaded I think Australia would consolidate the Eastern Seaboard (including Adelaide). And probably blow up all infrastructure to the mines in WA and let you defend yourself.