Going to war is too easy, far too easy. That is the one clear message from the Commons report on David Cameron’s 2011 war on Libya. It presents that venture as an ill-conceived vanity project, to dust the ingenu prime minister with some “Arab spring” glory. In reality it brought untold misery to a country to which Cameron promised peace and democracy.

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The immediate purpose of the war was to save “hundreds of thousands” in Benghazi from imminent massacre, after their uprising against Libya’s leader, Muammar Gaddafi. The certainty of this massacre was dubious. So too was the legality of Britain’s (and France’s) aggression. The military and intelligence communities could not see the point. Nor could Barack Obama. Mission creep was inevitable, and the outcome was certain to destabilise not just Libya but its neighbours. It was none of Britain’s business.

This is not hindsight. Plenty of people said it at the time – clearly not loudly enough. As the foreign affairs committee says, Cameron’s defence of the intervention was drenched in mendacity: that it was strictly humanitarian, that it was just a no-fly zone, that it was not taking sides in a civil war, that it was not aimed at regime change. As for his promise to cheering crowds in Benghazi, that “we will stand with you as you rebuild your country and your democracy”, that was a patent lie. Already he could not even visit Libya’s capital, Tripoli, as it was plunging into factional fighting and chaos.

Facebook Twitter Pinterest ‘As for Cameron’s promise to cheering crowds in Benghazi, that “we will stand with you as you rebuild your country and your democracy”, that was a patent lie.’ Photograph: Stefan Rousseau/AFP/Getty Images

The fallacy of intervention by bombing alone is that it can morally distance the aggressor from the consequence of his actions. To bomb a regime out of existence has the same outcome as invading it. Those who destroy authority, law and order in other people’s countries have an absolute obligation to restore them.

The essence of imperial power projection, from the Roman to the British empires, was total commitment. Armies came, saw, conquered – and stayed to hold the peace. Conquering was easy. It was holding the peace that was hard, and eventually bled empires white. As in Baghdad in 2003, so in Tripoli in 2011: the destruction of authority was more cataclysmic than any other worst-case scenario. Cameron had seen this in Iraq, yet in Libya he cut and run. He sowed the seeds of chaos and left anarchy in his wake.

We know, and knew then, that Islamist fanaticism feasts on tribal discord. By unlocking the doors of Armageddon, Cameron admitted fanaticism to north Africa. As such he threatened Tunisia, Algeria and Mali. He also provided a lawless corridor through which hundreds of thousands of refugees could make their way to Europe. He thus ironically fed the Brexit cause and his own downfall. He and his advisers must have given some thought to this.

The Blair-Cameron interventions since the turn of the 21st century have, with American help, destabilised an entire arc of the Muslim world. Millions have died and been driven from their ancestral lands, on a scale reminiscent of historical human catastrophes in eastern Europe, Russia and China. Of course, this “could” have happened anyway, as it happened in Lebanon and in the Iran-Iraq war. But it happened far worse after the interventions began.

Much of foreign policy is founded on false parallels. The Libyan venture was said to be justified because intervention “worked” in former Yugoslavia. That is true. But Yugoslavia was a patchwork of European provinces. The wars worked only through massive commitment on the ground, with the two rebel provinces, Bosnia and Kosovo, becoming de facto EU protectorates. Bosnia is reputedly the most subsidised state on Earth. Libya had no such luck.

The other proclamation is that Syria today “proves” that not intervening is even worse. This is madness. Syria was a tragedy of its own making, but it was immeasurably prolonged by the west arming President Bashar al-Assad’s enemies and enabling a Sunni-Islamic State statelet to arise in Iraq; that and Russia’s massive support for Assad. Intervention has been the death of Syria. The idea that British bombers and (heaven forbid) ground troops would have prevented such internecine strife is absurd. If we want to help Syria, we should welcome its refugees.

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What the Commons report does not do, any more than did Chilcot over Iraq, is ask why Tony Blair and Cameron were able to rush to war with so little thought given to consequences, and with so little opposition from within the political community.

British leaders of the postwar and cold-war eras were chary of wars of intervention. They knew that violence mostly escalates and begets more violence. Harold Wilson, Ted Heath and Margaret Thatcher steered clear of Vietnam, Congo, Cambodia, Bangladesh and Ethiopia. The present generation is more gung ho. The past 15 years have seen Britain fight more wars abroad than the previous 50. Not one has involved national security. What changed?

The answer is that these “wars of choice” have been essentially ventures of prime ministerial self-esteem. As Chilcot showed, in the case of Iraq the decision to send armies overseas was regarded by Blair’s colleagues almost as his personal privilege. Cameron likewise craved a personal “victory”, and afterwards visited Benghazi to take credit. There were reservations from the defence and intelligence chiefs. But a feature of bombing intervention is that nobody on “our” side gets hurt. Intervention can seem almost an exercise, Olympic Games with whizz-bangs.

In these circumstances, caution has no constituency. During Libya, Britain’s much-vaunted national security council concerned itself with legalities and logistics. As in Iraq, when war drums sounded and the press was cheering, no one had time for the tedious topic of postwar reconstruction. Sceptics were dismissed as wimps, appeasers and do-nothings. Everyone was high on the narcotic of glory.

It is to Cameron’s credit that, in the case of war on Syria in 2013, he did ask for the check of a formal parliamentary vote, to confront what he absurdly claimed was “a direct threat to this country”. To parliament’s credit, it refused him. That did not stop the Commons last year returning to the fray by voting to bomb Syria after all. That has hardly made any difference. But the thesis was, as they said of Gaddafi, the old one: that nothing could be worse than Assad. Want to bet?