Loading Replay Replay video Play video Play video One big reason? Australia already has the protection of the United States nuclear umbrella. Under this system, the US pledges that if anyone should launch a nuclear strike on one of its allies, Washington would retaliate against the aggressor. So to suggest that Australia now needs its own atomic arsenal is to suggest that there has been a fundamental breakdown in trust. In short, that the US alliance is dead. The four fissile firebrands - Hendy, White, Dibb and Brabin-Smith - don't press this as an urgent priority. But they don't want Australia to be caught unprepared if it should become so. North Korean leader Kim Jong-un with US President Donald Trump. Credit:AP

But hold on. Why now? Isn't this exactly the wrong time to be laying such plans? Doesn't this week demonstrate that the US can act to deal with a hostile nuclear state? Didn't Donald Trump's summit with Kim Jong-un just reduce a threat for the US allies in the region, including Australia, which falls within reach of Kim's long-range missiles? There are two key points here. First, the text of the brief document that the leaders signed does say that North Korea "commits to work toward complete denuclearisation of the Korean Peninsula". But this is neither new nor convincing. A former US nuclear negotiator with the North Koreans, Republican David Asher, who led the North Korean activities group in the White House of George W. Bush, says: "For the President to say that the nuclear threat has been eliminated is, I think, unwise. If he's wrong, it'll be on him." Asher, a scholar at the Centre for New American Security, says: "I have hope, but after dealing with the North Koreans for 25 years, it's not a promise I personally can have great faith in." Asher has a litany of first-person examples of Kim Dynasty duplicity. Malcolm Turnbull and Donald Trump at the White House in February. Credit:Alex Ellinghausen

The consensus in Canberra is much the same. Although Turnbull has commended Trump for giving it "a red-hot go", he says that we need to see whether Kim actually delivers. The briefings that the security agencies gave Turnbull and other ministers this week were summarised by one participant as "it's complex, we need to wait and see". So the first point is that no one can yet know whether Trump has actually de-fanged a dangerous enemy. But the second point is what everyone does know now - that Trump is prepared to trade away the interests of an ally if he thinks it will help him get a deal with an enemy. Trump announced that he had promised Kim he would stop the big military exercises that the US conducts with South Korea twice a year. This is not necessarily a bad idea and may be a useful concession to show US goodwill. The joint exercises began in 1968 after Pyongyang sent a team of 31 commandos to assassinate South Korea's president in his official residence, the Blue House, in Seoul. They failed but got within 100 metres of their target. The military manoeuvres were designed to show US and South Korean unity, commitment and readiness. South Korea's Moon Jae-in with Kim Jong-un in North Korea last month. Credit:AP

The problem? The cancellation was news to South Korea's President, Moon Jae-In. It was news to another keenly interested US ally, Japan's Shinzo Abe. And it was news to Trump's own military commanders, who were in the middle of preparations for the next exercises, two months away. And in announcing the end to the manoeuvres, Trump adopted the language of the North Korean propagandists. Pyongyang has long railed against the exercises as "provocative war games". The US has never called them war games nor described them as provocative; Trump did both. It seems that Kim put the demand to Trump in the negotiating room and Trump agreed on the spot. He agreed to a demand by an enemy without consulting his ally. "It is urgent to make bold decision," Kim told the US leader, in the words of the North Korean official news agency, and Trump bought it. This was greeted with delighted incredulity in Beijing. Because this is precisely what the Chinese Communist Party has sought for many years. Professor Shi Yinhong, of the People's University in Beijing, said that Trump's pledge to halt military manoeuvres was almost "too good to be true" from China's point of view. Illustration: Jim Pavlidis Credit:

Why does China care? Because one of its greatest strategic aims is to separate the US from its allies. One of America's greatest assets is that it sits at the centre of a global alliance system embracing more than 40 nations, including most of the world's major economies. China, by contrast, has a only couple of rather unimpressive allies, Pakistan and North Korea. Shi drew the connection: If US troops in South Korea were to stop the military exercises, it could cause allies to lose confidence in Washington and undermine the entire US military presence in Asia, he told America's National Public Radio. For China, this is victory on every level. "We see a clear pattern of Donald Trump turning against his allies," says a close student of Trump foreign policy, Tom Wright, a senior fellow at the Brookings Institution in Washington. "He's generally hung his allies out to dry." Loading Just in the last two weeks he has harmed US alliances with Britain, France, Germany and Canada, putting punitive tariffs on their exports and insulting Canada's Justin Trudeau on top, calling him weak and dishonest.

He upset his allies at the annual G7 summit by proposing that Russia be restored to the group's meetings, when the G7 is supposed to be ostracising Putin for invading Ukraine. Trump has inflicted so much political damage to America's European and Canadian alliances that "the community of North American and European nations forming the nucleus of the alliance that won the Cold War for the West is closer to breaking up now than at any time since the 1940s" in the assessment of Walter Russell Mead, an American scholar. "And," says Wright, "he completely sidelined Japan" with this week's Kim summit. It seems that there was only one US ally who had been able to persuade Trump decisively to change US policy, and even that has turned sour, says Wright. South Korea's Moon was the one who persuaded Trump to try directly negotiating with Kim, yet in those very negotiations Trump ended up trading away a South Korean interest. "Moon thought he could ride the tiger, control where he went, but didn't realise the tiger goes where the tiger wants to go," as Wright puts it. "He brought Trump into this but then lost control." A photograph released by German Chancellor Angela Merkel's office captured the tense relations at the G7 summit. Credit:AP

Why does Trump consistently act against the interests of his allies? Wright, who predicted just this pattern of behaviour before Trump was elected, explains: "In his 30-year history of talking and writing about this stuff, Trump has always been more aggravated by America's friends than its enemies. "He has been consistent about this for 30 years. It's not sophisticated or complex, but he is much more ideological than people think: interdependence is a bad deal for America." Trading partners will cheat America; allies will free ride on America's military budget. Australia has been unscathed so far; Wright says that this will likely change only if some disagreement emerges. Trump isn't so systematic to work down a list of allies he must alienate, but he will "react to what's in front of him. It's possible to sneak on by." The only time he will turn against a US rival is if he thinks that rival is directly threatening the US with attack, according to Wright. Otherwise, he's happy to deal with America's enemies: "He's open to deals, he worries about commitments." Which is how he manages to make concessions to North Korea while sidelining the interests of South Korea. Trump went further, saying that he wanted one day to withdraw the 28,000 US troops that provide an American "trip wire" across the Demilitarised Zone separating North from South.

If the North should invade, the US forces will be engaged automatically, the wire tripped, guaranteeing America will come to Seoul's defence. Trump said this was a matter for the future; South Korea's Moon wishes he hadn't raised it at all. If Trump's North Korean gambit works, he will have a serious achievement. If it fails? Says Asher: "The irony of the North Korean denuclearisation deal could be that everybody else decides to go nuclear. If it fails and Kim remains in power and countries doubt our commitment, then what's to stop Japan or South Korea or Australia going nuclear?" It could lead to "mass nuclearisation - it's a very bad position, 20 countries in the region with nukes, like 20 people in a room all pointing guns at each other". These are, of course, imponderables, possible futures that no one hopes for but governments need to plan for. Hendy and White and Dibb and Brabim-Smith may be tending towards alarmism, but they want Australians to think about the world after the American-led alliance system has passed into history. An American journalist, Jeffrey Goldberg, writes in The Atlantic this week that he asked a number of unnamed White House officials whether there is a Trump doctrine in foreign policy. One, described as a senior official with direct access to the President and his thinking, replied that there is. And it is: "We're America, bitch." History is in the making.

Peter Hartcher is international editor