Lawrence Freedman: America may find itself stuck with a long-term role in Afghanistan

'We'll now see if the famed network of caves making up bin Laden's redoubt is indeed formidable'

The arrival of US marines at Kandahar airport signals that the war has moved to a new stage. First, it indicates that the defeat of the Taliban is considered to be so close there is no risk of American forces getting caught up in a prolonged and bloody battle to gain control of Afghanistan. Second, it suggests the Americans do not think that Osama bin Laden has escaped and that by moving quickly and decisively they can catch him.

The course of this war has followed a line dictated as much by the possibilities for local bargains as the state of the military balance. The ferocity and the incessant nature of the US bombing led the Taliban front lines to crack, and as they cracked opportunities were made available for what turned out to be a very distinctive Afghan way of conflict resolution. This depends on coercive diplomacy, with protracted sparring to see who has superior power, before the hard bargaining begins on the terms of surrender – or, as likely, defection.

It only gets really nasty when the outcome of battle is uncertain. Should victory come by way of brute force, little mercy is shown to the losing side, with the occasional massacre pour encourager les autres. For those with the sense not to fight to the bitter end, defeat becomes rather like insolvency, with the faction in question soon trading under another name. Trading is often the operative word, for with territorial control comes the ability to take a share of all economic activity, including trafficking guns and drugs. Religious fervour soon seems to be of less importance than ethnic identity and commercial opportunity.

As a result of this approach, and taking into account the country's bloody history, the reported strength of the belligerents and the amount of territory that has changed hands, the fighting so far has been less bloody than might have been expected. The apparent rout of the Taliban after the initial fall of Mazar-i-Sharif did not so much result from a loss of fighting spirit as political cohesion. This explains the speedy loss of Kabul, where one might have expected a regime fighting for its survival to make a stand.

Now the focus is on Kandahar. Reports from the city do not suggest vast numbers of fighters. The American presence at the airport may well have some helpful coercive effect, although there is no indication the Americans are interested in getting involved in frontal assaults. Calls to join other Pashtun factions to help maintain some political balance within the country and influence the Bonn negotiations may be as important.

Meanwhile, the characters the Americans have been really chasing have, as likely as not, taken to the mountains. We may now get a chance to see whether or not the famed network of well-provisioned caves, stores, underground passages and obscure paths that are said to make up bin Laden's redoubt turn out to be as formidable as advertised. Clearly the hope is that the Afghan way will carry this campaign forward to its final destination, through a combination of high bribes and the settling of old scores, followed up by US forces.

What the US forces will not do is provide the sort of peace-keeping force that Britain and the UN still suspect may be necessary if Afghanistan is to have a stable government. The Americans have made it clear they do not see this as a useful role for their troops, but they may not be able to avoid the issue. In Kosovo, Nato had forces ready to move in as soon as the Serbs capitulated, and before the Kosovo Liberation Army was able to get itself established. The British attempt to repeat the move this time, by grabbing Bagram airport, failed because of the speed with which Kabul fell, the distrust of the local warlords of any international move that might cramp their style, and the reluctance of the Americans to get involved in any operation that could see their forces stuck for an indefinite period.

If the Americans and British had taken Kabul and other territories, they would have had a large say in the new constitutional arrangements for Afghanistan. Now, that influence will have to be earned through promises of economic and technical assistance. For this assistance to materialise, there must be confidence that it will be handled in a competent and non-corrupt manner. For the moment, however, the risk of anarchy, and the associated humanitarian distress, suggest the first priority will be to get a government in place. Those trying to broker a deal must deal with claims based on representation of substantial chunks of the population, against those based on actual control of territory.

If the proposed government is to have much authority beyond Kabul, the key question will be whether any sort of unified army can be created. The only alternative will be a peacekeeping force, but the task in this case may not be to mark the line between former belligerents, but to help a factionalised government establish itself in the country through organising factional disarmament. Without the US, any force may lack the clout to do the job. Also, while so far members of the Northern Alliance have acted with more restraint than many expected, the Americans have worked so closely with them that they have a stake in continued good behaviour.

For the US and its allies all this is not just a matter of whether they leave Afghanistan neat and tidy, and with some prospects of order and prosperity. They will expect, in addition, to use the opportunity to deal with the country's critical role in the international heroin market. Also, the position of the Pakistani government may become more difficult. It gambled that if it abandoned the Taliban in favour of the US it would not only gain much-needed economic support, but it would also be able to continue to influence developments within Afghanistan. Now it is alarmed at reports of the treatment meted out to Pakistani fighters found among the Taliban, the prospect of a hostile government in Kabul and of Taliban and al-Qa'ida fighters moving into its own tribal territories, which are already pretty lawless. If conditions become chaotic within Afghanistan, the US will find it harder to be confident that al-Qa'ida will not emerge from its bankruptcy boasting a new corporate identity, but with the old directors and the same mission statement.

It is another useful rule of thumb that the unintended consequences of any war are as important as the intended. Washington may find that the logic of events leaves it stuck with a substantial and long-term commitment to Afghanistan, well beyond anything it currently has in mind.

lawrence.freedman@kcl.ac.uk