The future problems for Australia will not be that we are "attacked" or "invaded" in the conventional sense. World food shortages from climate change will push people in other countries to take the risk and flood-in to Australia by whatever means they can. How can a submarine with missiles stop this mass migration?
Citizens of Madagascar are starving now. Many are living on cactus leaves and grasshoppers because of drought from changes in climate. Where will the citizens of the Maldives go if the drought continues for another year? (and yes, El Nino is predicted to still be around in 2022)
The population of Indonesia is 277 million. Where do you think these people will go if there is a food shortage, and they see lots of land in northern Australia not being cultivated ?
A defence department in a country usually designs its defence strategy around what it sees as the theme enemy. Our military is TOLD by the United States what our theme enemy is (i.e. China). Coincidently this involves throwing lots of money at the US to buy expensive equipment. Our real enemies in 10 years time could well be a) disenfranchised population in a fractured economy and b) dealing with the huge numbers of "illegal" immigrant settlers. F35's and nuclear powered submarines will not be much help then.
Start learning Indonesian, Malay, Japanese, or even Chinese. This could be your tool to adapt to the new changes. You can be sure that your DOD will be out there fighting more Don Quixote style wars and ignoring the real problems. The commitment by Australia to buy 100 x F35's, (which even the US defence department acknowledges are unsatisfactory) is treason by neglect. China needs us and we need China for our prosperity.
