Was the war worth it? After a series of rapid Taliban advances, fears have increased that the sacrifices of soldiers and civilians during 20 years of fighting may have been in vain.

This story is told by a journalist who was there. Like many others, he has been reflecting on the soldiers' mission, now that British and American troops have withdrawn, and the enemies they kept at bay are sweeping across the country. The Taliban have taken nine of the 34 provincial capitals, and are threatening others.

Among their conquests is the city of Pul-e-Khumri.

The cost of the war was enormous for the government's Western allies. US forces suffered over 20,000 casualties, including 2,300 deaths, while more than 450 Britons were killed. The bill for the American taxpayer was almost $1tnShort for trillion, is 1,000 billion..

But the suffering of the Afghan people was even worse. More than 60,000 members of the security forces were killed, as well as nearly twice as many civilians.

The reason for American and British involvement was simple. When the Taliban took control of the country in 1996, they allowed Al-Qaeda to set up camps where terrorists from around the world were trained.

After Al-Qaeda's attacks on the US2,977 people were killed in attacks involving hijacked aeroplanes. in September 2001, the Taliban were asked to hand over those responsible. When they refused, America and Britain sent in troops to support a coalition of anti-Taliban forces called the Northern Alliance. The Taliban were quickly defeated, and Al-Qaeda's fighters fled the country.

Since then, not a single international terrorist attack has been planned - so from that point of view, the invasion was a success.

Fatal mistake?

But, more than 1,000 people have been killed in fighting between the Taliban and the government in the past month. There are reports of Taliban fighters going from door to door and forcibly "marrying" girls as young as 12.

It is possible, too, that Al-Qaeda will return to the country. According to one expert, Dr Sajjan Gohel: "There is a real concern that Afghanistan could revert back into the breeding ground for extremism that it was in the 1990s."

A more optimistic view is that two decades of democracy and recognising women's rights have strengthened Afghans' aspirations, and made it harder for the Taliban to impose the fundamentalist state they sought. "The country is in a better place than it was in 2001," says Britain's Chief of Defence Staff, General Sir Nick Carter, "and the Taliban have become more open-minded."

Was the war worth it?

Some say, no. If - as seems more than likely - Afghanistan reverts to the country it was in 2001, with a repressive Taliban regime allowing terrorist groups to flourish, then thousands of soldiers and civilians will have died in vain. History has shown it to be a disastrous place to wage war, and America and Britain should never have attempted an invasion.

Others point out that, thanks to the war, an attack on the scale of 9/11 has never been repeated. Foreign jihadists are now considered less of a threat to the US than home-grown right-wing terrorists. A whole generation of Afghanis have grown up with an education which the Taliban would have denied them, and they are the key to the country's future.