For two successive months, the casualties in Afghanistan have reached record numbers. With the procession of flag-draped coffins from Brize Norton to grieving families throughout Britain, the questions over the effectiveness of the Nato intervention in Afghanistan and whether we are engaged in an unwinnable war become more persistent.

The process of stabilisation and construction, which is crucial to replacing the opium trade that funds the Taliban and fuels criminality and misery in the UK and elsewhere, has been plagued by the complexities of the country. The government's writ barely extends beyond the capital, corruption is rife and power is brokered along tribal lines. Given the scale of the failure of the strategy to eradicate poppy growing (a record 8200 tonnes of heroin was produced last year), securing the co-operation of tribal leaders who previously supported the Taliban holds out the best hope of progress.

Much will depend on Mullah Abdul Salaam. A Taliban commander who defected to the Afghan government, he was made district governor of Musa Qala in January in a move designed to demonstrate to other Taliban leaders that if they align themselves with President Hamid Karzai's government and accept the constitution, they will be rewarded with positions of power.

As the leader of one of the sub-groups of the dominant tribe in Musa Qala, Mullah Salaam has pledged to bring his armed tribesmen to fight alongside British forces. It is a significant move for the Kabul government and its western allies because for the first time they have been able exploit tribal divisions within the Taliban in Helmand. Defectors cannot be recruited easily; rumours that Mullah Salaam was planning to defect resulted in an assassination attempt last November and it will be a continuing threat. Stability in Afghanistan will ultimately require a political solution, and that cannot be achieved without tribal support.

Yesterday Gordon Brown refused to set an "artificial timetable" for withdrawal of British troops from Afghanistan, insisting they must remain to stop the Taliban "taking over" and al Qaeda "coming back". This follows the prediction from Air Chief Marshal Sir Jock Stirrup, the head of the UK armed forces, that the task of creating security in Afghanistan could last decades. It will be a long and difficult process, and success will depend on providing a better alternative to the Taliban. That requires roads (the Taliban begin where the roads end, said one observer recently), health centres and schools. A significant amount has been achieved, but at considerable cost, including the lives of 110 UK service personnel. Training Afghans to be an effective police force and putting in place structures for local and national government is a vital part of the military task. That a powerful leader believes that the development programme offers a better future for his people than the Taliban is a vital step forward. The British forces in Helmand must ensure that his belief is justified in order that other tribal leaders will follow his example.