SYDNEY (AFP) - Facing a wobbly ally in the United States and an increasingly bellicose China, Australia's military strategists are cautiously debating whether the country needs to consider developing its own nuclear deterrent.
For a long time, the country's defence forces had relatively little to worry about.
A century-old alliance with the US brought bankable security guarantees, while mineral exports to China ensured 28 recession-free years at home.
But US President Donald Trump's limited regard for alliances and Chinese President Xi Jinping's quest for primacy in the Pacific have put both pillars of Australian security in doubt.
"Far from being in a strategic backwater, Australia is very much now a state on the front line," said Dr Malcolm Davis, a military planner who has long called for a rethink of Australia's defence.
So far, the response from Canberra has been cautious: trying to preserve the alliance with the US while trading with the world's rising economic power.
But Dr Hugh White - former adviser to prime ministers, and a doyen of Canberra military analysts - believes it is time to get off the fence.
Amid arcane discussions about strategic autonomy, interests and capabilities, his book How To Defend Australia published this month has ignited a firestorm of debate with one simple question: "What about nuclear weapons?"
Dr White - a professor of strategic studies at the Australian National University - does not advocate for or against nuclear weapons, but says the question is becoming unavoidable.
Citing "big strategic shifts in Asia", he argues that "it is no longer clear that nuclear weapons would never make sense" to Australian defence.
"The strategic costs of forgoing nuclear weapons in the new Asia could be much greater than they have been until now."
Developing even limited deterrence would carry enormous economic, political, diplomatic and social cost - requiring Australia to withdraw from the Non-Proliferation Treaty and provoke neighbours.
But the vast nation-continent may be extremely difficult to defend alone, with a limited population and conventional weapons.
Dr White argues that without a cast iron guarantee from Washington, even the mere threat of a nuclear attack from China could "force us to capitulate in a conventional war".
DECADES IN THE MAKING?
The discussion is not completely out of the blue.
Dr White reports that for decades, Australian planners had quietly considered nuclearisation and worked on assessments of how long weapons would take to develop.
But until now, Canberra always decided that the price was too high, the risks were low and Washington had its back.
But Mr Trump's capricious temperament means half a century of policy could change with a single tweet.
Meanwhile, the threat outlook has changed.
Historical documents show defence analysts did not believe Australia would be targeted even in a serious nuclear conflagration between the US and the Soviet Union.
But bumping up against China seems much more likely.
And two regions inside Australia's sphere of interest have become geopolitical hot spots - the South China Sea and the South Pacific.
Australian warships and aircraft routinely patrol through the South China Sea, much of which is claimed by Beijing.
Even when Australian ships stick to international waters, they are shadowed and challenged by the Chinese military.
In one recent incident, lasers were shone at Australian Navy helicopter pilots taking part in a months-long naval operation, forcing them to land.
Prime Minister Scott Morrison has launched a diplomatic "step-up" in the South Pacific - hoping to re-engage in a region that increasingly draws Beijing's attention.
Critics have described Dr White's ideas as unaffordable, unrealistic and unnecessary.
"To put it mildly, the bipartisan political consensus on Australian defence policy is nowhere near White's position," Mr Sam Roggeveen of the Lowy Institute said in a review of Dr White's book.
Nonetheless, Mr Roggeveen went on to say that Dr White's view of a rising China and diminished US was "built on a dispassionate analysis" and was, to him, "convincing".
Not everyone is as convinced, but the fact that Dr White's ideas are being taken seriously speaks to a growing concern about Australia's place in the world.
In recent weeks, both a Chinese naval task force and a US assault ship have sailed into Sydney Harbour - the fact that both were invited did little to quiet public debate about how Australia relates to the world's two major powers.