Leading article: A cause worth fighting for

When Tony Blair promised in 2001 that Britain would stand by the people of Afghanistan, whom we had helped to liberate from the Taliban, most of us supported him. This newspaper did. The more he said how difficult it might be and that British forces might have to be committed to the mission for some years, the more we were convinced that we owed it to the Afghans to do more than simply install a puppet government, declare the job done and then leave them to the depredations of warlords and Islamist guerrillas.

Not that Hamid Karzai was a stooge of outsiders, of course. He was elected by an emphatic vote in the country's first free and fair elections. He has disappointed some of his own people since then, and he has occasionally offended Western governments and Western liberals with some of the nationalist and conservative poses that he has adopted for his own political ends. But the military intervention in Afghanistan in the 21st century was no imperialist adventure, as it had been for Britain in the 19th century and for Russia in the 20th. Nor was it comparable to the military intervention in Iraq that has done so much to colour British public attitudes to any of Mr Blair's claims to a moral purpose in foreign policy. Unlike Iraqis, Afghans tend to be pro-American; generally, the international force in Afghanistan has the support of the population.

For that reason, and because we recognised that making it harder for the country to be used as a base by jihadist terrorists was a long-term task – even if we hope it will not be the 40 years of which General Sir David Richards spoke last week – The Independent continues to support the British military role in Afghanistan. We do not agree with those who say we should do what we can to make today's elections as free and fair as possible and then leave. However much some people may have lost faith with Mr Blair, and however much some people may feel, after 204 British soldiers have lost their lives, that the task is hopeless and unrealistic, we believe that it is a noble cause.

That said, however, there is merit in the argument of Rory Stewart, the Foreign Office's "prince of the Marshes" who was in effect ruler of a large part of southern Iraq at an absurdly young age, and who has experience of Afghanistan. He, too, rejects the call for "troops out", but says the international force should adjust its goals, so that they are more realistically aligned with the quantities of troops and material deployed. With a total number of just 90,000, of whom 9,000 are British, there is a limit to what can be achieved. Mr Stewart suggests we accept that foreign troops cannot control the whole country, still less impose basic law and order and even less "reconstruct" the country, which often seems to mean turning one of the poorest nations in the world into a prosperous consumer society.

Just because our ambitions should be scaled back, however, is no reason for giving up. Britain and the rest of Nato must stay the course.