Leading article: India and Pakistan have a common extremist enemy

The slaughter in Mumbai has finally come to an end. But the political inquest into the atrocity is only beginning. Hundreds of angry Mumbai residents took to the streets yesterday to protest at the failure of the Delhi government to keep them safe. The Indian media, meanwhile, is asking pointed questions about how prepared the authorities were for such an assault.

This has already prompted the resignation of the interior minister and the national security adviser. It is quite right for Indian society to hold its leadership to account in this way. But at the same time it is worth remembering that, whatever the failings of the authorities in this particular case, it is unrealistic to expect India's government to stop every murderous-minded terrorist before they strike. It is hard enough in a technologically advanced country like Britain to monitor such fanatics. In vast, chaotic and still relatively poor India, it is next to impossible.

In the end, such attacks come down to politics. This was a politically motivated assault on the Indian state, and the key to stopping such atrocities occurring again will be a political solution to the virulent scourge of militant Islamism. The Pakistani connection of the terrorists who brought carnage to Mumbai is growing steadily clearer. One captured attacker has reportedly admitted to belonging to the Kashmiri militant group, Lashkar-e-Toiba, which has been supported in the past by the Pakistani intelligence services. Whether or not Pakistan will be discovered to have had a hand in this particular attack, it is clear that there will be no peace across southern Asia – from Afghanistan to India – until Pakistan is prevented from exporting and funding terrorists.

There is some hope. The government of Asif Ali Zardari in Islamabad has as much interest as Delhi in seeing the extremists of Kashmir and Pakistan's western territories suppressed. The fundamentalists have no more sympathy for Pakistani democracy than they have for the Indian variety. The horrific bombing of the Marriott Hotel in Islamabad in September and the assassination of Mr Zardari's wife, Benazir Bhutto, last year are testament to that. These two nations have a common enemy.

But they will also need outside assistance to defeat it. Washington made a crucial strategic error in the wake of the 11 September attacks by allying itself with the military rule of General Pervez Musharraf in Pakistan. It shored up a leader who was unable to take on the extremist elements in the country because he ruled, in part, with their support. The result was that Islamabad never purged the Pakistani intelligence services of their Islamist sympathisers. The covert support for militants continued. And if the recent US intelligence report stating that Pakistani intelligence facilitated the bombing of the Indian embassy in Kabul earlier this year is accurate, then it is going on even now.

The new administration of President-elect Barack Obama must insist that this comes to an end, on pain of a termination of American aid deliveries to Pakistan. More urgently, America must use its influence with India and Pakistan to cool relations between the two nuclear-armed neighbours.

Hillary Clinton is expected to be named as Mr Obama's new Secretary of State today. There will be no more pressing issue in Mrs Clinton's in-tray than helping the democratically-elected government in Islamabad rid the Pakistani state of the curse of Islamist extremism.