Donald Trump is running fast to escape the catastrophic war on Iran that he and Benjamin Netanyahu started four months ago. He is saying anything that appears to suit the moment. In fact, he clearly feels he can now ditch his friend, the Israeli prime minister. He is offering Tehran’s military regime a $300bn rebuilding fund, an end to economic sanctions and a promise not to interfere in its internal affairs. All this is declared a “major win”. If so, fine. The next 60 days of negotiations will be tortuous and unpredictable. But at least they are pointing in a plausible – and hopefully irreversible – direction.

For once, a US president seems ready to accept defeat in a potentially forever war before it gets out of hand. Iran is not to be another Vietnam, Afghanistan or Iraq. More than that, in the course of the past week, Trump seems to have soured on America’s closest ally. Furious at Netanyahu’s ceaseless bombing of Lebanon, he remarked: “You don’t have to knock down an apartment house every time you’re looking for somebody” – somebody to kill, that is – because “there are a lot of people in those apartment houses and they’re not all Hezbollah”. For all this moral grandstanding, Trump’s military forces, along with Israel, have killed more than 3,300 Iranians, according to the country’s authorities – among them more than 100 children in a girls’ school – and injured many more.

Trump in February was clearly driven by the same urge that has afflicted almost all recent American presidents, at least since the end of the cold war. It is simply the urge to display power. With an enormous military machine deployed in every corner of the globe, they cannot stop themselves intervening. Justification is almost an irrelevance. When the intervention is quick and neat, as in Kosovo or Kuwait, it at least can work. It was efficient in Trump’s recent decapitation of the Venezuelan regime.

More often, the giant gets trapped. Trump, once the great supposed non-intervener, was elected on a pledge to avoid such temptation. Nine years ago he gave just such a commitment in a passionate speech in Saudi Arabia. Washington interventions were over. “America will not seek to impose our way of life on others, but to outstretch our hands in the spirit of cooperation and trust.” He was cheered to the skies.

Trump’s blatant breaking of that pledge in February appears to have been a personal decision, triggered by his then friend Netanyahu. While the Israelis were assassinating Iran’s leaders, he would launch a massive bombing assault that would somehow lead the Iranians to rise up and topple their government. The justification was thin and sketchy: that the regime’s potential to make nuclear weapons would one day threaten US national security. It was effectively a repeat of the reason George W Bush and Tony Blair gave for their otherwise inexplicable 2003 invasion of Iraq.

Trump’s declared strategy for the war beggared belief. No coherent intelligence can have suggested that victory would be achieved in “four to five weeks”. Victory was regularly redefined. It might not be an Iranian revolution. It might be the destruction of nuclear weapons facilities, though they were supposedly destroyed last year. Or might it be the seizure of “nuclear dust” or perhaps just the massive destruction of Iranian state property? As in Iraq, it all seemed no more than a schoolboy excuse for going to war.

The task for America’s friends must now be to help Trump extricate himself from this debacle at speed. Tehran has merely repeated its longstanding promise to abjure nuclear weapons. It may have to accept that Washington will find it hard to control Israel’s attacks on Lebanon. That will not be easy. But as the settlement is clearly a victory for the Tehran regime, it would be wise for Iran’s leaders not to force this point.

The best outcome of the war would be the ending of sanctions and the opening of Iran to outside commerce and contact. This is far more likely to dilute the regime’s grip on society than any bombing. In the longer term, it will be the only path to political liberty in that country. Isolation has been counterproductive, further drenching Iran in the mythology of fundamentalist Islam and driving it into the arms of Russia and China. This could not have been more hostile to western interests.

This war should have done something else. It should have ended once and for all the theory that bombing other countries, their cities and civilians, somehow “works”. Ever since the second world war, the iron law of air forces has been that bombing somehow terrifies and demoralises populations into seeing the error of their ways. That it drives them to surrender and on to political action and rebellion. This belief in the potency of terror is no different from the strategy of groups such as al-Qaida.

The wonders of modern air war are such that the bombers persist in claiming precision in seeking military targets. They only kill “terrorists”. To that we can only say that they are lying. To an Iranian, as to a Palestinian or a Lebanese, bombing civilians is simply state terror. It is an attempt to effect a political outcome through violence and fear. I cannot think of a single case of this being achieved. In wars of aggression, its failure is normally cloaked by subsequent military action on the ground.

The seduction of massive bombing to a world power is easy to see. It can be swiftly staged. It makes a noise, is televisual and minimises casualties on the aggressor’s side. These qualities have long sufficed to distort military strategy. America believed in Vietnam that it could bomb the Vietcong “back to the stone age”. It was a failure. As in Afghanistan and Iraq, troops had to go into action on the ground. Yet Trump and his war secretary, Pete Hegseth, could repeat the stone age metaphor verbatim in Iran. The best that can be said is that they have soon realised their mistake.

So yet another lumbering attempt by America to recast the Middle East in its own image appears to have ended at appalling cost. It can only be hoped that the legacy of this war will be to discredit all such attempts.

• Simon Jenkins is a Guardian columnist