Patrick Cockburn: As Sangin shows, British troops were never geared up to make a lasting difference

British troops are well out of Sangin, where they fought against a classic guerrilla campaign with very little sign of lasting success.

The area, where a tenth of the British troops in Afghanistan suffered one third of total casualties, is symbolic of Britain's involvement in Afghanistan, as a bit player whose contribution was always going to have little effect on the outcome of the whole campaign.

There were never quite enough British troops to gain permanent control of Sangin, and the Taliban obviously sensed the vulnerability of British troops spread too thinly.

Roadside bombs could inflict a toll which was difficult to justify in terms of bringing an end to the war. In any case, nobody now expects the Afghan war to end with a victory for one side or the other. Even the American "surge" is designed primarily to rob the Taliban of the momentum they were gaining last year, so serious negotiations can start.

For the moment, such talks are a way off, which is scarcely surprising given that peace means ending a 30-year struggle in which Afghan ethnic groups have widely differing interests. Permanent peace will involve not only Afghans and Americans but Pakistan and India.

The only compelling reason for Britain to be fighting in Afghanistan is to retain its status as America's principle ally. Any suggestion that British troops are keeping the streets of Britain safe has always been demonstrably untrue. It is a long time since al- Qa'ida was based in Afghanistan and suicide bombers in the US and Britain appear to be motivated primarily by anger provoked by American and British military actions in Afghanistan and Iraq.

The idea that British forces could clear the way for good government for the people of Helmand has never made much sense. As American generals and diplomats have made clear, the weakness of the campaign by Western military forces in Afghanistan is that there is no civilian government ready and willing to move in. Opinion polls show that the majority of Afghans see the Kabul government as a racket aimed at extracting bribes. It might have been better if US and British troops had spent more time securing the main roads of Afghanistan rather than trying to root the Taliban out of their villages. What is most shocking over the past four years is the way the Taliban have taken control in areas where they are not popular and have limited forces.