A Trump victory would elevate these anxieties considerably. It seems unsurprising that certain analysts suggest it may no longer be wise for Australians to rely quite so heavily on the swaying bulwark of US military obligation.

Former prime minister Kevin Rudd is a leading sinocist. He believes China's President Xi will move on Taiwan the moment his generals advise him that the Peoples' Liberation Army, Navy and Air Force are very likely to overcome the Taiwanese and their combined allies. In Dr Rudd's view that moment may arrive as early as the late 2020s.

However, if Mr Trump is elected again, turmoil in Washington and a faltering economy in China may see President Xi's priorities shift. The Peoples' Republic of China military may be tasked with earlier subjugation of Taiwan.

Should this occur, Professor Hugh White has made it quite clear that any US administration will "... expect Australia to contribute the full range of our air and naval forces to the maximum extent of our capability". This is both a reasoned and ominous prediction. Armed conflict on this scale will not be restricted to operations somewhere to the north of Darwin.

Some in Canberra belatedly realise they squandered years devoted to the illusion that business with China was the key bilateral priority. Until recently, our politicians would rather not risk Beijing's wrath by making serious preparations to deter or at least resist the communists' appetite for coercion.

The journalist Peter Hartcher has several times identified this truth: each new trade deal has not been seen by Beijing as delivering mutual benefits. Each agreement has instead been viewed as a fresh point of pressure with which Beijing may narrow Canberra's sovereign prerogatives.

In the early hours of a Sino-US crisis in which Mr Trump is US commander-in-chief, he may attempt to mollify President Xi by "cutting a deal". However dubious it may seem today, withdrawal of key US forces to Guam or even Hawaii is probably credible in Mr Trump's arguably frail mind.

He is also likely to dismiss American ANZUS obligations. This act would satisfy his notorious hostility to alliances with loyal democracies while further appeasing Beijing. Abandoning Australasia would be consistent with his unpredictable if curious warmth towards dictators. And America alone has always been a Trump organising principle. Once the US nuclear umbrella has been folded and conventional American forces sent eastward, Australians would face bleak prospects.

Over the middle term of 25 years the Chinese Communist Party seems unlikely to tolerate a democratic and free Australia. Before 2049 they anticipate obedience from an obeisant Australia located within their widening Indo-Pacific sphere of influence. Professor Rory Medcalf has evaluated this risk in a thoughtful manner and arrived at a perhaps overly sanguine conclusion. The key here is a future geo-strategic perimeter to be drawn by Beijing. If the communists succeed, this will probably become a more or less contiguous frontier facing a declining American sphere of influence from which Australia is to be excluded.

What is to be done?

At least three unpopular steps will be necessary if Australia is likely to survive intact in 2049. The defence budget requires prompt funding of at least 3.5 per cent of gross national product. A large and flourishing sovereign arms industry will be another indispensable ingredient. (Long-range missiles and air defences seem compelling). Third and most sensitive will be conscription of hundreds of thousands of healthy young men and women required to form a formidable citizen army. From Sweden to Singapore, there are several models from which Australia may learn.

The CCP and its acolytes will probably characterise this author's opinion as alarmist hyperbole or their quaint favourite of "Cold-war thinking". Meanwhile, the communists' global influence narrows others' freedoms through a vast modus operandi: debt entrapment, corruption of elites in weaker democracies and intimidation of ethnic Chinese citizens in stronger democracies; coercion of target economies through oscillating trade manipulation; a medieval if effective appetite for hostage diplomacy, offensive deployment of armed PRC fishing fleets and ambiguously attributable (or otherwise) cyber operations; and - much like organised crime groups - threats to the welfare of innocent persons and their families, some of whom live in targeted countries like Australia.

Amongst international government organisations, the PRC remains a diligently thorough subversive while its military expands at a spectacular pace. A particular concern arises from Beijing's erratic grey zone provocations against Australian navy and air force personnel. Sooner or later, these operations will almost certainly cause loss of life to either or both sides. What then?

Amid recent signs of positive change the ball remains firmly in our court.