Long after you leave Zimbabwe images linger in the mind, harrowing and ineradicable. An emaciated old woman making “soup” from weeds for her orphaned grandchildren; desperate parents foraging in the bush for a handful of desiccated berries; young men defying crocodiles to catch a handful of tiny fish in the Zambezi; the corpses of cholera victims trussed up in black plastic sheeting; the ubiquitous and debilitated Aids victims; perfunctory funerals in Harare's cemetery while, all around, fresh graves are dug.

The pathetic attempts to grow vegetables on scraps of common land; the queues desperate to withdraw a few pennies from banks before their money loses all its value; the listlessness and despair of a crushed and broken people, the anguish of priests, doctors and aid workers overwhelmed by this tsunami of suffering...

There are other images, too. Of once bountiful farms plundered then abandoned by Robert Mugabe's cronies, fields vanishing beneath the encroaching bush; of Zanu (PF) fat cats and their playboy offspring speeding around Harare in sleek Mercedes, or stuffing themselves in restaurants; of opponents beaten, tortured and killed; of Mr Mugabe and his profligate wife holed up in their heavily guarded estate, oblivious to the misery of their people, while Western NGOs inadvertently prop up a pernicious regime by providing the rudimentary services - food, water, healthcare - the failed state can no longer deliver.

“Enough is enough,” Gordon Brown declared as the West worked itself up into one of its periodic lathers last month. But no one, it seems, is prepared to contemplate the one guaranteed means of removing Zimbabwe's President: military intervention by a multinational force.

Nothing else has worked. Mr Mugabe has shown not the slightest intention of honouring his commitment to share power with Morgan Tsvangirai and the Movement for Democratic Change. South Africa has singularly failed, despite repeated international exhortations, to exert real pressure on Mr Mugabe to step down. Thabo Mbeki, its former President and the Southern African Development Community's mediator, has been downright complicit in sustaining the regime.

There will be no popular uprising against Mr Mugabe - three million of Zimbabwe's best citizens have fled the country and the rest are too weak, cowed and preoccupied with survival. A palace coup is improbable - the leaders of Zanu (PF)'s bitterly feuding factions appear to recognise that if Mr Mugabe falls, they all do. There have been no repeats of the riots by underpaid soldiers that briefly raised hopes last month. Some advocate a fuel blockade, but that would merely compound the suffering of ordinary people while the regime would undoubtedly find ways to circumvent it.

Which leaves military intervention - an idea from which, after Iraq, the world instinctively and understandably recoils. But is it really so unthinkable? You could equally well argue that if there were ever a case for regime change, for using military power to better the world, Zimbabwe is it.

First, it is eminently feasible. No great force would be required. The Mugabe regime, like a tree hollowed out by termites, is just waiting to be toppled. It is sustained by security forces whose middle and lower ranks are almost as penniless, starving and demoralised as the citizens they are meant to suppress. You see numerous soldiers and policemen hitchhiking on the highways, and in the privacy of a car they readily voice profound disgruntlement. It is inconceivable that they would fight to defend the regime, even if they had the weapons, fuel and transport. Most would melt away at the first sight of a foreign force. Any fighting would probably be over within hours, and the bloodshed would be minimal.

Second, there is a popular and legitimate government waiting to take over. Nobody seriously disputes that Mr Tsvangirai and the MDC comfortably won the presidential and parliamentary elections last March despite all Zanu (PF)'s violence, intimidation and vote rigging.

Third, it is immoral for the world to stand by, wringing its hands, in the face of such manifest evil. The 2005 UN World Summit agreed that the international community bore a responsibility to protect populations from genocide and other atrocities when their own governments failed to do so. What is happening in Zimbabwe is not far short of genocide.

More than half the population would starve were it not for Western food aid. Life expectancy has plunged to 39 years - the lowest in the world. Aids, cholera and other diseases sweep away the chronically malnourished. While the regime loots what is left of Zimbabwe's wealth, a third of the population has been driven out, 90 per cent of those that remain are jobless, and the currency is rendered worthless by an inflation rate measured in quintillions of percentage points. Any opposition is ruthlessly crushed.

The arguments against military intervention are easy to predict. It would set a precedent. South Africa would object. If Zimbabwe, why not Sudan or North Korea? Intervention would smack of Western imperialism. To which the answers are, in turn: I hope so; tough; because Zimbabwe is doable; and that any intervention force would have to include African troops. Kenya, Botswana and Zambia have all denounced the regime. Even Ethiopia might be tempted by the prospect of capturing its former President, Mengistu Haile Mariam, who lives there as Mr Mugabe's guest despite being convicted in absentia of genocide.

Once inconceivable, military intervention is still only a remote possibility. The political will does not exist. Already world attention has been diverted by Gaza, and Mr Mugabe - the “old crocodile” - has survived another crisis.

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