Focus: Part three The aftermath - Drugs, drought, warlords, mayhem. Peace is dangerous, bloody and costly

Camp Souter, a converted fertiliser plant on the outskirts of Kabul, is the headquarters of the British peacekeeping mission in Afghanistan. Here 300 troops handle engineering tasks for the International Security Assistance Force, Isaf, which maintains order and protects the interim government in the Afghan capital. They also patrol the area around the base, which is far from being a routine task: a few days ago a senior Afghan official was shot in the head just after British soldiers had gone by. He survived, but his attackers remain uncaught.

Camp Souter is named (with uniquely British irony) after Captain Thomas Alexander Souter, only survivor of the battle of Gandamack, fought in 1842. It was a chapter in one of the greatest disasters in British military history, the retreat from Kabul, in which the Army of the Indus was all but wiped out. Today's soldiers insist the locals are more friendly than they were in the 19th century, and that their experience of street patrolling in Northern Ireland and the Balkans has served them well.

Those in charge of Isaf appear to agree, since the British force will soon take responsibility for a much larger slice of Kabul, a city which – despite the removal of the Taliban regime and its al-Qa'ida allies at the end of 2001 – still sees frequent gun, grenade and rocket attacks. Two American soldiers were seriously injured in one of these, while a suicide bombing aimed at Germans killed three Afghans. In September a car bomb in Kabul killed more than 30 civilians, on the same day that an attempt was made to assassinate Afghanistan's interim president, Hamid Karzai.

The skills the British peacekeepers acquire in keeping the lid on this devastated, desperately poor and volatile capital will be valuable if, as expected, they are needed in another area of operations. If there is an early assault on Iraq, peacekeeping could well end up being the main task of the British forces still being deployed to the Gulf. What happened in Afghanistan could be repeated in Iraq: the Americans quickly win the war more or less on their own, or with whatever local proxies they can recruit, but Britain and the rest of the coalition have to take responsibility for putting the country back together afterwards.

"You cannot engage in military conflict and ignore the aftermath," said Tony Blair last week. In Kosovo, Afghanistan and now possibly Iraq, he has stuck to the theme – take military action if necessary, but then ensure the international community stays to help build and pay for reconstruction and rehabilitation. "Getting rid of the Taliban was not the end for me," he assured a committee of MPs. As the influential Centre for Strategic and International Studies in Washington said last week, "Recent experience ... has demonstrated that 'winning the peace' is often harder than fighting the war." So how well are we doing in Afghanistan?

New arrivals at Camp Souter are told that most areas of the country are still unstable. There is a lack of aid from international and non-governmental institutions; the warlords still rule their own districts, where they control aid supplies; the Taliban remain in small pockets throughout the country; more than two decades of war has left millions of mines and unexploded munitions.

More problems could be added to the list. No one needs to be told, for example, that Osama bin Laden and Mohammed Omar, the Taliban's mysterious leader, remain at large. Despite some rain in recent months, Afghanistan is still in the grip of a four-year drought, though that has not stopped a resurgence of opium poppy growing. Since the strict Taliban lost power the opium harvest has roughly doubled to 3,000 tons a year, the highest in the world.

Many of these problems date back to the West's neglect of Afghanistan after the fall of Communism, while others, such as the return of the warlords to the areas they held before the Taliban pushed them out, were deemed necessary evils in the "war on terror". Countries which sold nuclear and chemical weapons technology to Iraq in the 1980s were at the same time encouraging the Afghan resistance to engage in drug-running, to pay for the war against Moscow's puppet regime in Kabul. All this has magnified the task of trying to make amends.

The 51st Highland squaddies patrolling around Camp Souter say local people often express their appreciation. For all the mayhem, Isaf has made Kabul the safest part of the country, which has attracted hundreds of thousands of Afghans from elsewhere. But there is no question of the force moving into other cities, despite pleas from President Karzai and belated political support from the US, because the international community does not have the financial, political or military will to confront hostile warlords on their own turf. "It will never happen," said Colonel Russ Wardle, the British commander in Afghanistan.

Instead, efforts are being made to spread the "Isaf effect" by sending teams of 50 to 60 internationals to eight regions, in the hope that they will plant the seeds of greater stability and encourage foreign aid agencies to come in. The Americans have launched the first in Gardez, a Pashtun stronghold close to the areas where the remnants of al- Qa'ida and the Taliban leadership are thought to be hiding out, but want other nations to lead the rest. Britain is considering leading one team.

If that is a small start, Camp Souter itself is evidence of Britain's commitment: turning it into a peacekeeping base was the biggest building project in Afghanistan since the fall of the Communist regime in 1992. Under an agreement with the interim government the camp will remain in British hands for at least five years. It is likely to be considerably longer before it is handed back to the Afghans for possible use as an agricultural college.

The British commander insists that billions of dollars of aid are coming into Afghanistan – "billions from the Americans, millions from us and the Germans, more from the Japanese" – adding that Paul Wolfowitz, the hawkish US Assistant Secretary of State, was in town recently. "He assured everyone that Afghanistan hasn't been forgotten."

But how long will such a commitment survive war in Iraq, when Afghanistan becomes yesterday's conflict, as happened to Kosovo and Bosnia in their turn? In recent years the British military has been forced to become as expert in peacekeeping as it is in fighting. Once again, our service men and women may well find themselves staying on when the US Marines have gone home, to keep the peace as Baghdad is rebuilt.