North Korea might be a monstrous regime, but it was a problem that the West could probably afford to ignore. It’s getting harder to ignore now. Since Kim Jong-un succeeded his father six years ago, he has made striking progress with a weapons programme that’s designed to provoke America. Last year alone, he managed 24 missile tests and two nuclear tests — as if to provoke Barack Obama into a response. It failed. Last month, Kim tested a missile that he says was capable of reaching the American mainland.

Earlier this week, he promised to fit it with a nuclear warhead. Then he finally got the reaction he wanted, as Donald Trump promised to unleash “fire” and “fury like the world has never seen”. Kim seems delighted. His psychotic regime is based on the idea of being on the brink of war with America and he badly needs a US president willing to play along. So he is now promising to fire missiles towards the US island of Guam, daring the Donald to retaliate. To those who have long suspected that Trump’s short temper and strange machismo could lead America into war, the nightmare seems to be starting. But this time, it was not just a tantrum.

Trump’s “fire and fury” language was unnecessarily provocative but it is part of a fairly coherent government strategy. For almost a quarter of a century, Pyongyang has been stringing America along: agreeing to talks, promising not to develop weapons in return for some bribes, taking the money then developing the nukes. Deals were struck with Bill Clinton in 1994, George W Bush in 2007 and Barack Obama in 2012 — all of them aimed at encouraging, or simply bribing North Korea away from its nuclear ambitions.

The failure of this policy was evident when the latest intercontinental missile was tested, of a size and power that might reach Los Angeles. Kim might not have the technology to fit the missile with a nuclear tip capable of withstanding the journey, but that’s the obvious next step. So is it really so unreasonable for the Trump administration to conclude that there’s not much point in returning to the old cycle of talks, treaties and treachery? Crucially, this is about more than America. If its cities are at risk from a North Korean nuclear strike, a future president might conclude South Korea is simply not worth going to war to defend. If America chooses isolation — hardly an impossibility — then the US nuclear umbrella might no longer cover its allies in Asia.

In which case, other nations there might well feel the need to acquire nuclear weapons — leading to a situation where peace in the region could depend on the sanity of whoever rules in Pyongyang. It’s a scenario so terrifying that it even scares the Chinese — and this is where those around Trump sense there is a breakthrough. They suspect that, for the first time, Beijing may genuinely see the North Korean regime as more of a liability than an asset. For some time now, China has pretended to be shocked at its neighbour’s behaviour, while being secretly pleased that there is someone to destabilise America and stop the creation of a united Korea.

So Beijing doesn’t mind North Korea being a giant prison camp run by the mafia, as long as it is stable. A war would be unthinkable for China, and might see millions of refugees coming over its 1,368km (850-mile) border with North Korea. If the regime collapses, it might unite the whole peninsula. But this has never really been in prospect because Beijing has been confident that the US would not do anything too rash. With Donald Trump in the White House, this is a dangerous assumption to make. So Trump’s rhetoric is intended for Beijing, not Pyongyang. He is trying to persuade the Chinese govern ment that Kim really has pushed things too far, and his officials are saying the same. James Mattis, the defence secretary, has said Kim is “acting in ways that could end the regime”.

Joseph Dunford, the chairman of the joint chiefs of staff, has said it’s “unimaginable” for the US to permit “a capability that would allow a nuclear weapon to land in Denver”. But if this did happen, then what? If America was frozen by the threat of a nuclear strike, and left South Korea to the army that is already gathered 45 minutes away from Seoul, what next? This, the threat of American withdrawal, is the part of the US strategy that Trump will never talk about — but others do. HR McMaster, Trump’s national security adviser, has started to speculate openly about what Asia would look like without American protection. It would be quite easy, he said last weekend, to imagine a nuclear-armed North Korea, South Korea, Japan, China, Russia. “Is that what China wants? Is that what Russia wants?” he asked. China has agreed to help impose sanctions on North Korea, and — he says — it now accepts that it should use its huge influence not just to stop Kim developing new weapons but have him dismantle existing ones. You might think this a rather optimistic strategy, but it’s not entirely crazy. So: how do you solve a problem like Korea? The Trump administration has a fairly clear answer: you persuade China that the stakes really are too high, and that it’s time to act. You point out, behind the scenes, that American military intervention might be bad — but American retreat might make things even worse. Here, at least, there is a method to Donald Trump’s madness: as he says, no strategy in the last 20 years has worked with North Korea. This one just might.

—The Telegraph Group Limited, London 2017

Fraser Nelson is the editor of the Spectator and a columnist for the Daily Telegraph.

The Daily Telegraph