Is this the turning point? A deranged US president and an Israeli prime minister facing prosecution are seeking to entice the armies of the world into the stupidest war of the 21st century. Israel’s strike this week on Iran’s South Pars gas field was clearly meant to provoke an Iranian retaliation so massive as to ensure a ferocious response from Donald Trump. Thus escalation beckons. This is how small wars become big.

There is only one way of calling a halt. It is for Trump and Israel’s Benjamin Netanyahu to stop bombing Iran. Yet both leaders clearly see themselves as trapped. Trump, having already claimed to have won the war, now feels lonely. Though he has amassed the largest aggressive force of modern times, he pleads with his one-time allies to come and give him moral support. But Trump started this war. He must face the wound to his pride that may go with stopping it. He must then complete the harder task of getting Israel also to stop.

Meanwhile, Britain should play no part at all. Its security is not remotely threatened. Whatever evil Iran poses to British interests, war is no response. Nor is it Britain’s duty to judge and replace foreign regimes, a task at which its recent record is deplorable. How to contain modern terrorism may be a longstanding challenge, but aerial bombardment offers no answer.

Yet Keir Starmer is sending senior military planners to Washington to help Trump plan how to reopen the strait of Hormuz. That assumes no agreement on Iran’s part to its peaceful reopening. This is in addition to Britain having already made British bases available to US bombers, laughably for “purely defensive purposes”. Such a slide into collaboration is how George W Bush ensnared Tony Blair in Afghanistan and Iraq. It might be called strategic seduction. Starmer must not stumble down the same path as led more than 400 British soldiers to their deaths in Helmand.

Trump claims that Britain owes the US a debt in return for Washington’s nuclear deterrence of Soviet Russia under Nato. This shows how incoherent has become the jargon of international defence, where “national security” glibly justifies any act, however disproportionate. Trump maintains that Iran had become “an imminent nuclear threat” to the US and was “weeks away from developing a nuclear weapon”. This was as false as Bush’s similar claim for Iraq’s weapons of mass destruction. Trump himself had boasted that Iran’s nuclear enrichment sites had been destroyed by his bombing of Iran last June.

These arguments easily become lost at times like this in the military rhetoric beloved of rightwing politicians and macho commentators. It is a world of shock and awe, of existential threats, multilateral responses, military targets and collateral damage. It supposedly justifies the killing from the air of thousands of innocent people. The only winners are military establishments, defence lobbyists and populist demagogues. Theirs are the songs that have summoned nations to war down the ages. Their tunes are the best – at the time.

Starmer now finds himself in exactly the predicament that should have been ruled out after Britain’s Suez fiasco in 1956. Then, an assault on Egypt to assert British control of the Suez canal failed to topple the Cairo regime. It ended when Washington told the British prime minister, Anthony Eden, that he had gone mad. Britain accepted the message that its imperial outreach was at an end, but it was reluctant to completely withdraw. It could not see itself as just another European country minding its own business. The overseas bases remained, as did the yearning to intervene.

Hence, 70 years later, Britain still finds itself spending millions on its “defence” in the Indian Ocean and the Mediterranean. Imperial memorials in Cyprus and Diego Garcia entice leaders, as Blair would say, to “punch above our weight”. Britain joined the Iraq war supposedly because of an “imminent threat” merely to its base in Cyprus. As for the latest row over the sovereignty of the Chagos Islands – it is beyond absurd.

And hence Downing Street still hankers after the White House phone call, the special relationship, the tariff deal, the intelligence swap. When the US commits an illegal act or a monumental blunder, somehow Starmer feels he cannot respond, as did other European leaders, and condemn Trump outright. He nervously equivocates.

Two weeks ago, there was perhaps an argument for seeing Israel’s decapitation of the Tehran regime as being in the same category as Trump’s toppling of Nicolás Maduro in Venezuela in January. It could be explained as an overnight operation with a planned and limited outcome. The past three weeks have seen no such outcome. War is now open-ended.

As it is, in the past week I have changed my mind on whether the king’s state visit to Washington should proceed. There should be no outright cancellation – it was to celebrate a bond of peoples, not governments – but it surely cannot proceed while Trump’s aggression continues. Britain’s monarch cannot be seen shaking hands with a man of such violence.

The bombing must stop. For the time being, nothing else matters.