Leading article: A formidable Afghan adversary

The attack by the Taliban on the heart of government territory in Afghanistan is strategically significant – the latest in a series of increasingly bold strikes on Kabul. Its gunmen penetrated the very heart of the heavily protected capital and got to within a hundred metres of the presidential palace in which Hamid Karzai was swearing in members of his new Cabinet.

What the timing of this well-planned and co-ordinated assault shows is that the Taliban are a group with a long-term political plan rather than just a fractious coalition of warlords bent on defending their patch. It underscores the extent to which this hardline Islamic movement has regrouped and, despite ever-higher numbers of foreign troops, have steadily extended their influence. Vast parts of Afghanistan are today vulnerable to levels of violence which the country has not seen since before the US invasion of 2001.

It all shows how fragile is the political situation not just in Afghanistan but throughout the Pashtun areas which straddle the border into Pakistan – a country with nuclear weapons which the international community fears might one day fall into the hands of the Taliban or their al-Qa'ida allies. And it underlines that there is no real alternative to the West's present approach to a dramatic increase in the number of its troops while at the same time increasing efforts to bring greater social and economic development to the area. Victory in Afghanistan will not be won by military force alone, but by making Afghans feel safer. A key part of that is training and strengthening the capacity of the Afghan army and police.

The one reassuring element about yesterday's attacks was that Afghan security forces took the lead in responding and, from all accounts, did so reasonably competently, bringing the situation under control within hours.

But the Taliban are proving themselves to be formidable political as well as military adversaries. It is why, for all the West's reservations about the petty bribery, nepotism, clannishness and clientelism of the Karzai regime, it has not much option but to continue to support it. It is a case, to quote Hilaire Belloc, of keeping hold of nurse for fear of finding something worse.