Welcome to 21st-century war, liberal style. You do not fix an objective and use main force to get it. You nuance words, bomb a little, half assassinate, scare, twist, spin and make it up as you go along. Nato's Libyan campaign is proving a field day for the new interventionism. Seemingly desperate to scratch another Muslim itch, Britain's laptop bombardiers and their tame lawyers go into a daily huddle to choreograph the latest visitation of death on some wretched foreigners.

Each day the tacticians tot up a gruesome calculus of wins and losses. Wednesday's defection of Libya's foreign minister, Moussa Koussa, somehow cancelled out two days of retreat by the rebels towards Benghazi. That retreat cancelled out a weekend of victory over Gaddafi's army along the northern highway. Nato bombing cancelled out rebel ineffectiveness. Everything is stalemate punctuated by surprise.

Meanwhile the legal niceties border on the absurd. We cannot kill Gaddafi, unless we describe killing as "all necessary measures". We observe an arms embargo, except apparently if the arms are going to our side and are thus "protecting innocent civilians". Guilty civilians are unprotected. We are forbidden from injecting "a foreign occupying force of any form" into Libya, except if it is a "special force" and aiding the bombing with targeting intelligence. The bombing of Gaddafi's compound and the witnessed killing of civilians in Sirte clearly breached UN resolution 1973. But who cares? As George Bush and Tony Blair found, you can drum up an international lawyer to defend anything.

Gaddafi's survival is ostensibly insane. He is the tinpot dictator of a tiny country that Nato could topple in a day. It could bomb his palace, take out his tanks, land paratroops on his airport and ship in reinforcements. Libya is not Iraq or Afghanistan. Nato could set up a client regime, as in Bosnia, secure the oil and give two fingers to the Arab world, as the west always does when its interest so requires.

Instead we have the ludicrous position that Nato can save Benghazi by taking out a tank column and then laying a bombed strip to the west. But all this does is encourage reckless rebels to drive towards Tripoli and die. The maxim is old as the hills. No war can be won from the air. A temporary balance of advantage can be awarded to one side, but pilots can only destroy. Bombs are inherently crude tools of war. They cannot seize and hold land.

At present Nato strategy appears to be to prolong civil war by bolstering the weaker side. It is the equivalent of refereeing a bare-knuckle fight so as to keep the contestants on their feet and still punching. Stalling Gaddafi's advance on Benghazi appears to have prevented its fall. Whether there would have been a genocidal massacre, as interventionists maintain, is not known. There would surely have been bloody retribution against ringleaders, which is what dictators do to those who cross them. But then Gaddafi, Assad of Syria, Mubarak of Egypt and Hussein of Iraq all did ghastly things to their enemies, usually while the west was cosying up to them.

Holding the ring for someone else's civil war is a bizarre justification for intervention. It is a distortion of the UN's peacekeeping role – indeed it might be termed war-keeping – and an abuse of Nato's supposed purpose, to defend the west against attack. Even setting those objections aside, any humanitarian gain is moot. Iraq and Afghanistan were Muslim dictatorships in a state of suppressed civil war when the west intervened. The result was hardly peace, tranquillity or an easing of tribal tension, rather more destruction and bloodshed. Yet these interventions were claimed as "humanitarian".

The projection of massive military strength against weak foreign states is assumed by western powers with the same bland assurance they showed in the 19th century. The end of the cold war seemed to release an urge way beyond the relief of human suffering, an urge to use military might to reorder the world in the west's own image.

The foreign secretary, William Hague, last week rattled every sabre against "governments that block the aspirations of their people, that steal or are corrupt, that oppress and torture, or that deny freedom of expression and human rights". This is a licence to attack virtually anyone you choose, to a degree not contemplated in the corridors of the Foreign Office since Palmerston, and not even then.

Hague may claim "it is not for Britain to dictate who should rule Libya", but why then is he bombing the place? There are instances where limited power projection has served a strictly limited purpose, as with the Kurdistan no-fly zone prior to 2003. But most interventions are preludes not to democracy but to partition, as in Kurdistan, Timor, Bosnia, Kosovo, Macedonia and possibly now Cyrenaica, or eastern Libya.

Gaddafi may have seemed a plausible victim for the latest intervention. Compared with Ivory Coast, Zimbabwe or the Democratic Republic of the Congo, where far worse atrocities are committed or threatened, Libya passed the usual tests. It was small, bombable, had "war on terror" connotations and was not sub-Saharan Africa, which, Sierra Leone aside, always seems beyond the interventionists' pale. Libya was "doable". It may yet be done. As the mission creeps, as all missions do, something called victory will demand some sort of ground troops to aid the rebel cause. There would be dreadful bloodshed, because bombs and shells always miss their targets. If Gaddafi can somehow be killed or otherwise disposed of, there will be some rudimentary puppet state, probably a sitting target for Muslim fundamentalists, gangsters and terrorists. Libya could be an oil-rich Kosovo.

I want nothing to do with this. I would send any amount of humanitarian aid to those in distress. But the dispute of eastern Libya with Gaddafi is not my dispute. As for the interventionists, if they want Gaddafi gone, as they constantly claim, they should get on with it, and not hand him yet another victory "over fascist imperialism" as they did by bombing him in 1986.

Such action would be opposed by other undemocratic Arab regimes, but they are surely next on Hague's list for regime change. Indeed some, such as Syria and Yemen, are of far greater strategic importance than Libya. David Cameron claims, bizarrely, that Britain's vital interests are at stake in the Libyan civil war. Eden said the same before Suez. But if that is so, Cameron should act accordingly. Who dares, wins.

The trouble with liberal interventionism is that it lacks the courage of its neo-imperialist conviction. It claims to know what is best for the world and glories in bombing to get its way. But when push comes to shove it backs off. So we have just a few bombs on the road to Benghazi, one Tomahawk on Gaddafi's compound, a few shells to terrorise Sirte, a handful of RPGs to keep the rebels from despair. It makes us feel good. If this is liberalism, you can keep it.