Lawrence Freedman: The US must conquer its fears and let the Northern Alliance attack Kabul

'The worry is that once they enter the city the fighters will commit acts of retribution and plunder'

The victory of the Northern Alliance at Mazar-i-Sharif has, for the moment, calmed the "wobble" that was starting to affect the coalition war effort. It came as commentators were wonder whether the Taliban were, if anything, stronger than they had been at the start of October. Now the mood has switched and the question is whether or not the Northern Alliance should aim to take Kabul in a rush.

From the moment after 11 September when attention began to focus on the problems of extracting Osama bin Laden from Afghanistan, the challenge for the Bush administration has been to synchronise moves on the political and military fronts. Initially, the Americans went for a high-risk military strategy to sustain a low-risk political strategy.

They hoped to avoid excessive dependence on any particular Afghan faction or member of the international coalition, by looking for a quick military fix, relying on strategic bombing and special force operations to undermine Taliban resistance and encourage defections. As the Taliban collapsed, the Americans would install a new, broadly based and UN-sponsored government in Kabul, possibly even including ex-Taliban "moderates". Their own forces, supported only by the reliable British, would start the search for Osama bin Laden's mountain redoubt.

The reason for the "wobble" was that it had become apparent that special force operations required far better logistics and intelligence than available and that the air raids, after the few genuinely important targets had been struck, were doing more harm than good. The Afghan people were angry with the Americans because of civilian deaths while the Taliban fighters were feeling even more confident because they had largely survived unscathed. Coalition partners were getting irritated at having been assigned a largely cheerleading role, and attempts to forge a new political order for Afghanistan were thwarted by a combination of traditional rivalries and uncertainty over the seriousness of the American intent.

The new approach involves a much lower-risk military strategy although it carries potentially greater political risks. The reduced military risks come about because the air campaign has become focused rather than speculative and geared to land operations. This has required close co-operation with the Northern Alliance.

The results have been impressive. Mazar-i-Sharif is a real prize, providing control of major highways and two airports. If the Americans can make these serviceable then they begin to establish their own forward operating base and create opportunities for an even more focused and responsive air campaign. The winners have few reasons to fear a counterattack as the Taliban seemed to have made their own strategic decision to fall back to predominately Pashtun areas, including Kabul, to make their stand. Their positions to the east and west of the city now look vulnerable.

Progress on the southern strategy has been less impressive. Attempts to get support among Pashtuns have faltered on the lack of credible local leaders, distrust of the Uzbeks and Tajiks at the head of the Northern Alliance, and the strength of local Taliban control. Furthermore, Taliban strategy may well be to play the Pashtun card for what it is worth as they abandon the territory of minority groups, aiming to keep Kabul and their other stronghold, Kandahar.

The pace of war is always unpredictable. Few expected Mazar-i-Sharif to fall so quickly, yet Kabul could take longer than expected. This will be a far tougher military nut to crack. The defences are better organised and able to exploit the mountainous terrain, leading to a possibility of vicious fighting inside the city and some grim footage for the world's media (representatives of which were not around to watch Mazar-i-Sharif fall). With the local population far less ready to switch sides, US air support will be crucial.

This creates a dilemma for the Americans as they are caught by the problem of the military campaign running ahead of their diplomacy. President George Bush, standing beside Pakistan's President Pervez Musharraf, implied that the Americans do not want the Alliance to take Kabul, but rather to lay siege to it. Both presidents are worried about the installation of a narrow-based government with inadequate Pashtun representation, as well as the nagging worry that once they enter the city the Northern Alliance fighters will commit acts of retribution and plunder.

The Americans might be able to influence the progress of the battle for Kabul, but will they really be able to bring themselves to hold back? The advantages if the Taliban lose control before the winter – and Ramadan – are enormous. Washington could claim that its strategy was working, sufficiently to allow the tempo of the controversial air campaign to be reduced.

The absence of serious anti-Taliban activity in the south means that nobody else could take the city. Any attempt by the Americans themselves to fight their way into Kabul would take time to prepare, prompt sharp internal resistance by giving a Soviet-like appearance of a foreign army of occupation, and cause severe casualties. So there is no alternative for the moment to a Northern Alliance offensive and its leaders are unlikely to be impressed by calls to wait for a military breakthrough before a political one has been achieved. They are more likely to be stopped by evidence of fierce Taliban resistance.

Having moved to a northern strategy the Americans may therefore have little choice but to try to see it through, hoping that potential Pashtun defectors in the South will change sides once they are convinced that the war is going against the Taliban, and that General Musharraf will decide to balance the Northern Alliance not by blocking it but by encouraging anti-Taliban activity in the South.

The first "wobble" of this war has been overcome but the next could start if the battle for Kabul turns out to be vicious and indecisive, with the third just coming into view with the question of whether these military successes really get the Americans closer to Osama bin Laden, who remains the main target of all this activity.

The author is Professor of War Studies at King's College, London