Do nuclear submarines mark Australia's return to forward defence?

Is Australia's nuclear-submarine programme changing its doctrine or returning it to defence in depth?

It is probably a return to defence in depth, reversing the earlier concentration of defensive reach close to Australia.

Australia's retreat from forward defence began before the Cold War had actually ended. Removing carriers and F-111 Aardvarks left the country relying on forces whose reach concentrated defence much closer to Australian territory. Modern cruise missiles can threaten the continent from great distances, so intercepting an adversary only once it enters the range of shore-based aircraft is too late. Nuclear submarines restore a way to operate at range and form part of an unacknowledged return to defence in depth.