Leading article: The harsh truth: this is a long, hard struggle

With Gordon Brown's announcement that UK troops are to be pulled out of Iraq, thoughts inevitably turn to Britain's other major overseas deployment. Has the time come to withdraw from Afghanistan too? To answer this, it is necessary to go back to 2001. The US was justified in taking military action to depose the Taliban after the 11 September attacks on New York and Washington. The Taliban had hosted the al-Qa'ida plotters, and refused to give them up. Unlike in the case of Iraq, military action was justified in international law and proportionate. Nato and the United Nations were also right to make a commitment to help to rebuild the country and prevent the Taliban returning to power.

To say that things have gone badly would be a scandalous understatement. The writ of Hamid Karzai's government does not extend far beyond the capital, Kabul. A recent study found 54 per cent of the country to be under Taliban control. And the suicide bombing campaign of recent months demonstrates that they have adopted the deadly tactics of the Iraq insurgency.

Failure in Afghanistan can be ascribed to a variety of reasons. Some of the blame lies in local circumstances. Afghanistan is a perennial failed state. Its infrastructure has been destroyed by years of civil war and foreign invasions. And Pakistan's lawless tribal regions have provided a base in which the Taliban have been able to regroup. But more of the blame must lie with the West, distracted and demoralised by the disaster in Iraq. Too little aid has been delivered. Not enough wells have been dug. Too few roads have been built. The policy of destroying the opium crop has alienated Afghan farmers. So has the US Air Force's bombing of Pashtun villages.

Gordon Brown was right to promise more aid and reconstruction on his visit to the country yesterday. He is also right to argue that the Western focus should be on winning public support for Nato forces and President Karzai's administration among ordinary Afghans. A good way to start would be for Britain and others to buy up the country's opium crop to make medical heroin supplies, as proposed by the Senlis Council.

But it was wrong for Mr Brown to hint that the re-capture of Musa Qala by a joint force of US, British and Afghan troops yesterday will be a turning point in the struggle against the Taliban (just as he is wrong to argue that British military withdrawal from Basra means that stability and peace has been restored to southern Iraq). If the past six years have taught us anything, it is that winning battles against the Taliban is relatively easy. It is winning the war that is the difficult part. The likelihood now is that the Taliban will withdraw for the winter and re-emerge in spring.

As well as aid, Afghanistan needs a new political and diplomatic initiative if lasting progress is to be made. The West must support President Karzai's talks with Taliban leaders. The Taliban is not a homogenous group, but a diverse coalition of tribes and interests. The goal of negotiations should be to persuade the more moderate elements to switch sides. The UN must also persuade Afghanistan's neighbours, Pakistan and Iran, to help the search for a political settlement. Moscow and India have influence in Afghanistan too. They should be prevailed upon to use it.

Yet even if this new approach were to bear fruit, it is impossible to see how Afghanistan can be anything other than a long-term commitment for Nato and Britain and one that will require great cost and sacrifice for the foreseeable future. If Mr Brown believes this, it is time for him to spell it out: we are in Afghanistan for a long, painful haul.