9/11 - A bloody legacy

The 'war on terror', which began with the attacks on the US, is five years old. It has killed tens of thousands and drawn British troops into conflicts around the world - but in Afghanistan, where the first victory was won, all the gains are in danger of slipping away

The West is fighting a crucial battle in the "war on terror", and British troops are in the front line.

British-led Nato forces are engaged in a make-or-break struggle in southern Afghanistan, where the biggest ground offensive in the history of the alliance was launched in Panjwayi district, near Kandahar, just over a week ago. The aim is to throw back a resurgent Taliban.

Yesterday, Nato said Operation Medusa had killed 40 Taliban fighters in the previous 24 hours, and several hundred more were surrounded. If the offensive succeeds, it will be a first step towards reversing the tide of instability that has engulfed an increasing area of the country and led to the deaths of 19 British military personnel this month (14 of them in an air crash).

But commanders admit it is an extremely close-run thing: if the offensive fails, the position of British forces in neighbouring Helmand province - where they were deployed this year with the then Defence Secretary, John Reid, expressing the blithe hope that they could complete their three-year mission "without firing a shot" - could become untenable.

Afghanistan was where the first victory in the "war on terror" was won. Less than three months after the 9/11 horror, al-Qa'ida's Taliban sponsors had been overthrown and Osama bin Laden was on the run. Yet tomorrow, when the fifth anniversary of the attacks on New York and Washington are commemorated, the world will reflect that Bin Laden remains at large somewhere along the border between Afghanistan and Pakistan. Mullah Omar, the Taliban's one-eyed leader, has also evaded capture, and his movement is regaining strength. What has gone wrong?

For General Sir Michael Rose, who led the SAS and commanded British forces in Bosnia, it is simple. "Having defeated the Taliban in 2001, the West then mistakenly shifted its effort and resources to Iraq, leaving most of Afghanistan insecure," he said. "This has allowed the Taliban to return." In other words, not only have gains in the real "war on terror" been dangerously eroded, the reckless detour into Iraq has made things worse. Far from hunting Bin Laden down, the West has been forced to prevent his allies re-establishing a foothold in Afghanistan.

After months of public denials by commanders and politicians, they are finally admitting that military forces in southern Afghanistan are stretched. Yesterday, as security forces in Kabul cleared the debris of the worst suicide bombing in the Afghan capital for two years - in which at least 16 people, including two US soldiers, died - senior military commanders from all 26 Nato nations were meeting in Warsaw to answer an appeal from Nato's supreme commander, US General James Jones, for up to 2,500 more troops at what he called "this decisive moment".

The Taliban cannot hope to win a head-on clash against Western forces, though General Jones admitted last week that the alliance has been surprised by the ferocity of the movement's response. The tactical initiative has been with the insurgents, who have kept Nato forces off-balance with hit-and-run attacks, suicide bombings and frontal assaults on isolated outposts in northern Helmand, where small British detachments have sustained a steady trickle of casualties as they fight off attackers.

"The fighting is extraordinarily intense. The intensity and ferocity ... [are] far greater than in Iraq on a daily basis," the commander of British forces in Helmand, Brigadier Ed Butler, said this month. Instead of calming an area by their mere presence, British soldiers have become a magnet for insurgents. Afghan forces remain unreliable, while the local population is equivocal, at best. The only secure point is the main British base, Camp Bastion, isolated in the desert north-west of the provincial capital, Lashkargar. One senior Western diplomat in Kabul called the situation "dire".

British and Irish aid agencies working in Afghanistan have been producing monthly reports on the state of the country since well before 2001, and the latest one makes grim reading. "The underlying security situation affecting the day-to-day mobility of the population, as well as the operations of the government and of the aid and reconstruction communities, is deteriorating in many areas," it says. "The Taliban have an increasing presence at the local level in large areas of the south and are in a strong position to threaten security, intimidate and also build a support base."

The big push in Kandahar province, where Canadian forces are doing most of the fighting, is aimed at regaining the advantage. The Canadians have chased the Taliban away in Panjwayi district many times before, only for the insurgents to seep back once Nato forces have gone. This time, officers say, the aim is to hold the ground once it has been captured. That, however, requires boots on the ground - and they are desperately short.

At the end of this month, Nato's commander in Afghanistan, Britain's Lieutenant-General David Richards, takes responsibility for all foreign forces in the country apart from a handful of Americans engaged in the hunt for al-Qa'ida leaders. General Richards has already indicated that he aims to take a more subtle approach than the gung-ho Americans, whose aerial bombardments are thought to have caused high civilian casualties.

In what is known as an "ink-spot" strategy, the intention is to start developing "Afghan development zones" in the south. Where the security situation has been stabilised, there will be a deluge of aid - first in the form of "quick impact" projects, and later of more sustainable development assistance. Nato and special forces will range around these zones, harrying the Taliban and preventing them upsetting the security balance within the safe areas. In the next stage, the roads between these zones will be gradually secured and the influence of the government extended around them. Like ink spots on a piece of blotting paper, the zones will grow until they merge together.

That, at least, was the theory when British forces deployed in Helmand this year. Amid relative calm, they would support development and drugs eradication in a province that contributes the largest share of the booming Afghan opium crop. It has not worked out that way. British commanders quickly dissociated themselves from efforts to destroy poppy fields when it would leave farmers no other source of income, but it was too late to prevent an alliance between the opium trade and the Taliban, which has destabilised Helmand and made aid work all but impossible. Particularly worrying is the apparent decision of a number of the province's powerful tribes to side with the Taliban.

In many areas, Nato has found the populace incensed by what General Rose called "American search-and-destroy tactics", but the danger is that troop shortages will force Nato, like the Americans, to make up in firepower what they lack in numbers.

The mission, in short, has changed drastically from the one outlined by Mr Reid in January. Hence Operation Medusa, which is merely the largest engagement in the second of a series of offensives against the Taliban. Backed with artillery and large-scale aerial bombing, they aim to weaken the Taliban decisively in battle and then prevent it reorganising and regenerating itself during the traditional winter break in the Afghan fighting season. That would theoretically mean a weakened insurgency next year and create permissible conditions for the "ink spots" to begin spreading in the south.

"In the relatively near future, certainly before the winter, we will see this decisive moment in the region turn in favour of the troops that represent the government," said General Jones. Commanders believe that a majority of the populace in the south is still waiting to see who will gain the decisive advantage. Once that becomes clear, the situation will change dramatically and quickly.

According to General Jones, it is a matter of a few hundred extra troops, though those are proving difficult to find. Many nations that have forces in Afghanistan, notably Germany, refuse to allow them to engage in all-out fighting, while Britain is already at full stretch. Even if everything goes according to the Nato chief's projections, that is just the beginning of the struggle to get back to where we were at the moment of victory in 2001.

Despite the weakness and unpopularity of the central government, Afghan security forces are an integral part of the strategy to reclaim the south. The Afghan army, which has so far trained 42,000 men, is better regarded than the police, but is of very uneven quality. One report from British trainers with a unit in Musa Qala claimed Afghan soldiers refused to fight, extorted money from local people, spent much of their time high on drugs and even threatened to shoot their British allies.

Nato will have no choice but to rely on them. The alternative is committing the sort of troop numbers the Russians put into Afghanistan. "It would require 40,000 or 50,000 troops to garrison Helmand," said one Western diplomat in Kabul. "We can't do that, and we don't want to."

For General Rose it is already too late. "Given the level of resources Nato has at the moment, and the strategy we are pursuing, we simply cannot win. The forces there can't achieve the objectives they have been given."