Paul Vallely: Tidy up before you switch off and leave

When troops withdraw from Afghanistan they will leave a country in disarray, but many have contributed to the mess

What kind of cook was the man who made the meals for Osama bin Laden? Was he the type who tidies up as he goes along? Or did he make a huge mess in the kitchen which he – or perhaps someone else – had to clean up at the end?

Either way, the Sudanese man who ran one of the kitchens in bin Laden's Star of Jihad compound in Afghanistan got 14 years in jail for his pains last week. Ibrahim al-Qosi, who was bin Laden's former driver as well as his cook, admitted providing support for terrorism. He was the first Guantanamo inmate to be convicted by the government of Barack Obama who once promised to shut down the detention camp. He is, in fact, only the fourth detainee to be convicted out of all the 800 prisoners the camp once contained, of whom about 180 are still behind razor wire.

So there's another triumph for democracy and the rule of law, though not perhaps for judicial transparency. Qosi has done a plea-bargaining deal which, Arab rumours suggest, will see him released in two years and returned to Sudan. The deal means that, however dirty he left the cooking pots, he may well have got out of tidying up at all.

But can the same be said of the British and American armies in the wars we have been fighting in Iraq and Afghanistan? Have we tidied up as we went along? Or have we created a great mess to be cleaned up afterwards?

Saddam Hussein's former foreign minister, Tariq Aziz, clearly thinks the latter. Those who start a conflict, he feels, have a moral responsibility to make restitution afterwards. He gave his first interview for seven years last week and – along with revealing that Iraq's pretence that it had weapons of mass destruction was to deter Iran rather than provoke the West – lamented that ordinary Iraqis were hungrier, sicker and less safe now than under Saddam. Last month was Iraq's deadliest since the height of post-war sectarian violence in 2006-2008. And the country is unable to form a new government after deadlocked elections.

President Obama, Aziz said, was "leaving Iraq to the wolves". The US army is to end its combat role in Iraq by the end of the month and will remove all troops by the end of 2011. "He cannot leave us like this," Aziz said. "When you make a mistake you need to correct a mistake."

That would mean, Iraq's army chief, General Babaker Zebari, suggested last week, that US troops must stay another decade because the Iraqi military might not be ready to take control till 2020.

Is cleaning up part of the duty of a warmonger? Or can we just push off when we've had enough and leave the locals to sort out the mess? Is clearing up part of the realpolitik penalty for being the loser?

Just War theory suggests that one of the necessary conditions for a moral conflict is that there must be serious prospects of success. In conventional wars, it was pretty clear what constituted success, but contemporary conflicts seem far less clear-edged. How do we now know when a war is finished and what level of rebuilding is sufficient?

Iraq does not have a stable democracy. It has short-term problems, like the fate of those in Camp Ashraf, where US and British troops have withdrawn protection from groups of Iranian dissidents opposed to the current regime in Tehran. It has long-term ones, like caring for large numbers of children born with deformities caused by depleted uranium from Allied shells.

There are lessons from Iraq we should carry to Afghanistan. Some of them are tactical. The British pulled out of their base in the Iraqi city of Basra on the supposition that violence would diminish. That was because 90 per cent of the attacks were against our soldiers. The assumption was that, if the troops went, so would the cause of the provocation.

What actually happened, apart from the move being portrayed by propagandists as a British retreat, was that the unchallenged militia which took over the city inflicted a regime of ritual rape, extortion and thuggery on the locals. It was not quite what Western politicians intended when they spoke of "allowing the Iraqis to run their own affairs".

There will be similar risks with the British intention to pull out of Sangin valley, where a third of all our troops have died in the current Afghan war.

The former Army chief, Sir Richard Dannatt, has pronounced that British soldiers have become like "flies in a honey pot" attracting attacks. Again the Taliban is poised to portray withdrawal as retreat. Again, the area is particularly dangerous because it contains a patchwork of rival tribes at the centre of Afghanistan's opium-growing industry, though this time the Brits are to be replaced by more than double the number of Americans under the Obama "surge".

But the lessons of Iraq are wider. We need to be honest about the bigger picture. Is it really true that if we don't defeat terrorism in Afghanistan it will run riot on our streets at home? It is just as likely that foreign wars fuel the domestic sense of Muslim grievance that nurtures terrorism in our own cities (just as armies of occupation prompt nationalist mujahedin to support the Taliban). And it is also a lot easier to defeat those terrorists in Britain where they can be tailed and their phones tapped, where our security services are operating in environments they know intimately, rather than on unknown foreign turf.

If the war is really, as some say, about the trans-Afghanistan gas pipeline – which when completed will run from rich oilfields in Turkmenistan and Uzbekistan through Pakistan to reach India and the West without reliance on Russia and Iran – we need a strategic discussion of risks and advantages. And we need to publicly debate the costs and benefits of having a puppet government in power in Kabul which is deemed to favour the West.

Barack Obama is a hostage to democratic ignorance on all this. He knows that if he just withdraws from Afghanistan there will be a sizeable group of US voters who will be led to believe that a wiser and tougher leader could have won, and Obama would risk losing the next election. Such voters are easy prey for the "we could have won if we had carpet-bombed the place and not fought with one hand tied behind our back" school of gung-ho patriotism.

That didn't work in Vietnam, of course, just as a conventional war didn't work in Afghanistan for Soviet Russia, even though it they two countries shared a land border. Afghanistan is called the "graveyard of empires" with good reason.

It is popularly said that in modern conflicts it is easy enough for a powerful army to win the war; the problem comes with winning the peace. In Afghanistan even that is not clear. Amid all the talk about nation-building and the transmission of democratic values there is still no answer to the most basic of questions: in Afghanistan, how will we know when we have won?