This is the moment in any war when peace goes dumb. The cause is just. The enemy is in our sights, and the provocation is extreme. Blood races through tabloid veins. It is white feathers for dissenters. The British government’s evident eagerness to bomb Iraq will be put by David Cameron to the House of Commons on Friday. With an election in the offing, Labour’s Ed Miliband dares not disagree.

The prime minister’s case, made to the United Nations on Wednesday, is that the Islamic State (Isis) rebellion is “an evil against which the whole world must unite”. No one would quarrel with that. Unlike Cameron’s abortive bid to bomb Syria last year, legality is covered by an invitation from Iraq’s hapless rulers in Baghdad and a refusal to bomb Syria. Past mistakes in Iraq, says Cameron, should not be an excuse for inaction. “We must not be so frozen with fear that we do not do anything at all.”

Nor should we be so intoxicated by war fever as to do the wrong thing. Iraq has been chief bomb target for western electoral machismo since Bill Clinton’s “Monica Lewinsky” air strikes in 1998. They initiated a decade of mendacity. Saddam Hussein’s weapons arsenal was declared eliminated, then it was not. After killing hundreds of civilians, Tony Blair and his cabinet declared that Iraq still posed “an imminent threat to Britain”. The subsequent war was said to have installed freedom and democracy in that country, another untruth. As the Royal United Services Institute concluded in a recent survey, far “from reducing international terrorism … the 2003 invasion [of Iraq] had the effect of promoting it”.

Those demanding a resumption of the bombing should explain how things are different this time – or be guilty of willing mission creep. So far they could hardly be less convincing. An indication is their resort to adjectival hysteria, Isis being variously repulsive, genocidal, atrocious, monstrous, unspeakable, satanic. Everyone seems to accept that air strikes “alone” cannot win. Yet everyone also asserts that there is no question of following them with ground attacks, which is the essence of coordinated war. They are merely to “degrade Isis assets”, mostly by demolishing empty buildings at vast expense. They are sending “a message” to someone or other.

Cameron’s strategy is apparently to leave local Iraqi forces to deliver victory. That might be reasonable, given that they are the most expensively trained troops on earth. But they have shown themselves useless. They have been given intensive bombing cover by the Americans for seven weeks, and Isis is firmly in place. Meanwhile, Cameron refuses to hold his nose and form a tactically vital alliance with Assad of Syria and with the Iranians. He appears not to want to win.

If Britain intends victory, Cameron should do what George Bush and Tony Blair did last time in Iraq and go full tilt at the enemy with planes, troops, tanks and guns galore – and to hell with the consequences. There is no logistical hurdle. Baghdad is begging to have British troops fighting alongside his army. So why is Cameron tying his own hand behind his back? It looks suspiciously as if this is all for domestic consumption. The new Iraq war has no strategy, not even tactics. It is a show, a token, a pretence of a strut on the world stage.

This dispute has all the menace of religious hatred down the ages, leading a retreat into tribalism and fear. Western intervention stirred it by undermining the secular, mostly Ba’athist, regimes that emerged after the second world war. The best hope now – indeed, the only hope – is that the regional powers can assert order, as Syria’s dictator did in Lebanon after the failure of western “policing” in the 1980s. Every corner is stiff with armies and weapons, including Turkey, Iran, the Gulf and Saudi Arabia. All are more threatened by Isis than is Britain. The Saudis have more than 700 jets, enough to bomb everywhere in sight. They should need no outside help.

Sooner or later Isis must disintegrate into its warring factions. The caliphate is an implausible construct. These horrors pass. Even the extremist Taliban in Afghanistan were mutating into a less vicious regime, until Bush and Blair came to their rescue by invading their country in 2001. In Iraq a pincer movement of Syria, Iran, Kurdistan and Iraq itself should one day grind Isis into submission. In doing so a new balance of power should be established in the region, the stronger for being self-generated.

Western air strikes are supposed to aid that disintegration. For once, British bombs are at least propping up an established government rather than toppling one. But they are far more likely to help Isis, by recruiting volunteers and turning Muslim opinion once more against the west. The resort to drones and the consequent killing of civilians will also win little political ground. Even the hawkish former US representative to Nato, Kurt Volker, warns that drones nowadays “allow our opponents to cast our country as a distant, high-tech, amoral purveyor of death. It builds resentment, facilitates terrorist recruitment and alienates those we should seek to inspire”.

The return to war will reinforce the politics of fear – which is the grimmest legacy of the Blair era in Britain. It has Cameron popping in and out of his Cobra bunker like a rabbit in a hole. Every government office, every train, every airport welcomes visitors to Britain with terror warnings and alerts. Cameron does this because he knows he can only get Britons to go to war by portraying Isis as a “threat to Britain’s national security”. Some Isis adherents may have criminal intent, but that is a matter for the police. Britain survived a far greater menace from the IRA without crumbling. Its existence is not threatened by jihadism. The claim is ludicrous. Cameron must have no faith in his own country.

The contrast between Asia’s eastern and western extremities is now stark, the one booming, the other descending into catastrophic instability and medieval horror. It is impossible not to relate this to two centuries of western imperialism and meddling. It strains belief that further intervention – through the crudest of all forms of aggression – can bring peace and reconciliation.

Islam’s wars are not Britain’s business. We owe their human victims all the aid we can to relieve suffering. We do not owe them our incompetence in trying to recast their politics. That is a task for the Arabs and their neighbours, not for Britain’s soldiers and taxpayers.