What on earth are we doing? I have not heard a single expert on Syria explain how dropping missiles on that country will advance the cause of peace or lead its dictator, Bashar al-Assad, to back down. It will merely destroy buildings and probably kill people. It is pure populism, reflected in the hot-and-cold rhetoric of Trump’s increasingly whimsical tweets. Heaven forbid that British policy should now, as it appears, be hanging on their every word.

We can accept that the chemical attack on a Damascus suburb was probably by war-hardened Syrian airmen, though rebellions do kill their own to win sympathy. But Britain too has killed civilians in this theatre. No, we don’t poison our own people, but we somehow claim the right to blow another country’s civilians to bits. Theresa May says that the chemical attack “cannot go unchallenged”, but that is a politician’s love of intransitive verbs. Who is to be the agency and under what authority? The time to punish the Syrian leadership is when the war is over. Outside intervention will make no difference to the conflict, except to postpone its end. That is doubly cruel.

France has proof Assad regime used chemical weapons in Syria, says Macron – live Read more

This crisis is already displaying the familiar preliminaries to a reckless conflict. Hysterical language cavorts with the machinery of militarism. It seeks reasons for violence, not for its avoidance. Thus there was no reason for Britain to go to war with Iraq in 2003, beyond a sabre-rattling competition between Tony Blair and America’s George Bush. Nor back in history was there a reason for Germany and France to fight in 1870. There was no reason for war in 1914, beyond the murder of an archduke in Bosnia. As AJP Taylor said of 1914: “Nowhere was there a conscious determination to provoke a war. Statesmen miscalculated [and] became prisoners of their own weapons. The great armies, accumulated to provide security and preserve the peace, carried the nations to war by their own weight.” I wonder what Taylor would have said of Trump’s “Get ready Russia” tweet.

Most wars nowadays follow a triggering of often casual alliances and obligations, and from the absence of any potent forum – or even “hotline” between leaders – through which disagreements and minor disputes might be resolved. Peace in Europe was roughly sustained for 50 years through the councils of the 1815 Congress of Vienna. Then it collapsed as if from exhaustion. The dread prospect now is that the post-1945 cold war settlement, roughly overseen by the United Nations, has outlived its usefulness.

Play Video 0:58 White House struggles to explain Trump's Russia missile tweet – video

All the more reason for the world to beware of proxy wars. Britain has no dog in the Syrian fight, which is a miserable resurgence of one of the oldest and bitterest Middle East clan feuds. Assad was able to call on Iran and Russia to come to his aid, and they have done so with grim effectiveness. The rebels on the other hand were encouraged to hold out by the moral support of the west, and by material support from the anti-Iranian Saudis. Syria has paid a terrible price. Further intervention now would be lunatic.

May seems trapped by Washington, as Blair was in 2003. It is clear that her advisers do not think bombing Syria is the best way to respond to a chemical weapons attack, but she seems reluctant to admit it. She claims not to need the approval of parliament in firing missiles. That convention dates from when monarchs and their generals needed discretion to ward off imminent threats to national security. There is no threat now. This is not a military but a foreign policy decision. Going to war has serious implications. It clearly merits collective approval, especially from a minority government.

Iran reiterates support for Syria in face of 'foreign aggression' Read more

In 2003, Blair sought the approval of parliament to invade Iraq, albeit on a lie. Shamefully he received it. In 2013, Cameron sought approval to fight Syria, and was mercifully denied it. May can avoid a Commons vote, but with a mere 22% of the public reportedly in favour of bombing Syria and 43% against, even the gain to her machismo might be at risk. The danger is what happens next. An eye for an eye suggests a more spectacular and photogenic repeat of Trump’s missile bombardment of last year. But the risk of killing Russian or Iranian troops is clearly high, and of provoking military retaliation higher still. Russia’s Vladimir Putin is said to be in a paranoid state, as tanked up on machismo as Trump and May. These are moments when leaders take on the raiment of commanders, and give themselves licence to decide policy alone. It makes the job of their colleagues in restraining them all the harder. In-house hawks have all the best tunes.

This shows how weak are the underpinnings of international peace when the balance of power is upset. Nothing in the current state of the world merits a superpower confrontation, only the narcissistic and belligerent personalities of certain world leaders. Victors in war have an obligation to show patience and restraint towards the defeated. Russia in 1989 was defeated, but the west has been gloating ever since. Russia in Syria is guilty. That is not the point. In this first crisis in east-west relations since the cold war, it seems we must now rely on Russia, not the US, to show patience and restraint. That is an ominous prospect.

• Simon Jenkins is a Guardian columnist

• This article was amended on 13 April 2018. An earlier version referred to the murder of an archduke in Serbia, however the Archduke Franz Ferdinand was assassinated in Sarajevo, the Bosnian capital.