Donald Trump is discovering the hard way that it’s usually wise to treat allies well – for if you treat them badly they’re less likely to help when you need them.

Despite several vainglorious boasts that he’s already scored a famous victory in Iran, Trump has been imploring America’s Nato allies to help reopen the Strait of Hormuz, through which a substantial chunk of the world’s seaborne oil and natural gas passes – at least it did until ‘defeated’ Iran closed it.

The longer the Strait stays closed, the more the global economy will be disrupted by soaring energy prices, with the risk of widespread recession growing by the day. So there’s a whiff of desperation in Trump’s request. But the Nato allies are hardly queuing up to lend a hand – for a list of very understandable reasons as long as your arm.

President Trump wants the allies to join in a war he started without even going through the motions of consulting them about why he was doing it or what war aims he hoped to achieve.

But now that he needs them, they’re expected meekly to fall in line. Unsurprisingly, none is prepared to oblige.

Almost three weeks into the US-Israeli attacks on Iran, Trump has yet to articulate what he sees as the endgame. The allies fear getting dragged into an open-ended commitment in which Trump alone will have the power to declare victory, whenever the mood takes him.

Yesterday Israel hit Iran’s South Pars gas field, the biggest such facility in the world. Tehran immediately vowed retaliation against oil and gas facilities in Saudi Arabia, the United Arab Emirates and Qatar. The closure of the Strait may be the least of the world’s worries if both sides are now going to take out vital energy infrastructure.

The whole Iran adventure seems to have been contrived by Jared Kushner, Trump’s son-in-law, and Steve Witkoff, a Trump business crony, in cahoots with Israeli Prime Minister Benjamin Netanyahu.

Kushner and Witkoff know much more about property development than war or geopolitics. Israel has its own agenda. No wonder the Nato allies are reluctant to get involved.

Nor does Trump’s conduct over the war to date inspire allied confidence. He began hostilities without giving much (if any) thought to how to keep the Strait open, even though it was clear that Iran would retaliate by closing it.

Washington sources tell me Trump was so convinced of US military superiority that he thought the tyrants of Tehran would topple before the regime ever got round to attacking the Gulf States or closing the Strait.

Why would the Nato allies now want to align with such epic stupidity? Especially since there still isn’t even the glimmer of a plan from Washington about how to reopen the Strait.

Trump is also paying the price for poisoning the well of allied goodwill. It’s only recently that he was disparaging and misrepresenting the role of allies who fought alongside the US in Afghanistan, their forces suffering many fatalities and life-changing injuries in brutal conditions (no ally more so than Britain). Why would they now rush to the side of someone so ungrateful and ungracious?

Moreover it was only in January that Trump and his MAGA bully-boys were musing aloud about invading a Nato ally if Denmark didn’t do as it was told and hand over Greenland to America.

Only in Trump World can you threaten allies with forcible seizure of their territory and still expect them, only a month or two later, to be loyal and supportive when you suddenly need them on the high seas.

Nor has it helped that Trump, bizarrely, sometimes treats America’s closest allies worse than its adversaries. Less than a year ago penal US tariffs were being slapped on friends from Europe to Canada to Japan while enemies like Russia were getting off scot free. Trump’s tariff obsession has been somewhat sidelined since. But allies were needlessly alienated.

For all these reasons and more there has been no allied rush to America’s side. Nor is there likely to be.

I take no comfort from writing these words. Ever since I studied American history and politics at university, worked as a White House correspondent for The Economist and bought a flat in New York where I still stay on regular visits, I have regarded myself as the epitome of the pro-American Brit.

It’s not always been a popular cause. As editor of The Sunday Times in the 1980s I was one of Ronald Reagan’s few fans in the British media. When Margaret Thatcher authorised US bombers to take off from England to launch air strikes on Libya in 1986 – a deeply unpopular decision – my newspaper was one of the few to back her.

I incurred the wrath not just of the Left but of High Tories sniffy about Reagan’s America. But I never regretted it.

So if even I can understand why the Nato allies are not now rushing to America’s side in the current conflagration, it’s fair to conclude Trump really has lost the room.

There will be a price to pay. Europe will suffer more from the continued closure of the Strait of Hormuz than America, which is largely self-sufficient in oil and gas.

And Trump will seek his revenge. He has a long memory and he will not quickly forget that when he snapped his fingers the Nato allies did not come running.

It will turn out to be a significant step on the road to a post-America Nato in which the US contribution is much reduced or even, eventually, non-existent.

The European allies, as they reject US overtures to help in the Gulf, need to brace themselves for all that will follow and what it entails.

Some European powers already get it. France’s advocacy of the need for ‘strategic autonomy’ in military matters has been vindicated. Germany is in the throes of a massive military Keynsianism, with over €500billion being spent on rearming and related infrastructure investment to create by far the biggest land forces in Europe. Even peace-loving Scandinavia is rearming fast.

But Poland is ahead of everybody. It now spends almost 5 per cent of its GDP on defence (twice the UK rate) to create armed forces of 300,000 regulars and 200,000 reservists. It is buying hundreds of K2 Black Panther tanks from South Korea plus M1A2 Abrams tanks from America. Its airforce is being modernised with F-35 fighter jets, South Korean combat aircraft and the biggest fleet of Apache helicopters outside America.

Before long, the combined might of Polish and German armed forces alone might be enough to deter any westward Russian adventurism. As for Britain, we have been reduced to the role of increasingly irrelevant spectator.

For most of the past 70 years we were Nato’s biggest military spenders after America. Now we are 12th and slipping further. Under the dead hand of Keir Starmer and Rachel Reeves, both of whom know nothing and care even less about military matters, the rise in defence spending has been pathetic.

They have committed to increase it to 3 per cent of GDP but refuse to publish a roadmap to show how or when we will get there.

Meanwhile we struggle to send one warship for the defence of Cyprus and have next to nothing to offer even if we wanted to help America reopen the Strait of Hormuz.

Trump and know-nothing blowhards around him started this war without Nato allies. They can finish it on their own. If they can. Nato has bigger fish to fry.

The beginnings of a post- America Nato can be discerned. In years gone by you would have expected Britain to be in the driving seat of such a venture. Instead we have opted to be on the sidelines, irrelevant and ignored – to the everlasting shame of Starmer and Reeves.