September 11 has turned out to be a good thing for America and the world

America is beginning to realise that in order to eliminate the threat to itself, it has to clean up the globe

In his memoirs, Henry Kissinger recounts a conversation with Jim Callaghan back in 1974. Both men were waxing melancholy about the ills of the human condition, and they finished on a grim note. Callaghan: "I think life is getting worse, Henry." Kissinger: "I think you are right." Callaghan: "I don't know what sort of age we're ... going to pass through, but historians like yourself ought ... to tell us how ... this next half century is going to look.'' Kissinger: "I'll tell you ... I'm glad I'm not going to be running part of it. It's going to be brutal.''

Almost at the mid-point of Lord Callaghan's half-century, 11 September appeared to vindicate Dr Kissinger's conclusion. The casual slaughter of so many innocents in a great Western city was sanguinary testimony to the frailty of our civilisation. It also seemed to prove that life was indeed getting worse.

Yet that is only part of the story. September 11 was a tragedy, but not a disaster. Intended as a threat, it turned into a warning. Long before the end of James Callaghan's 50 years, historians may have concluded that by alerting America to the dangers it faced at a moment when it was still possible to take effective counter-measures, Bin Laden did mankind a service.

On 10 September, America was no less powerful than it is now. The Bush foreign and defence teams were no less able: among the most formidable set of advisers any President had ever assembled. But all that potential strength seemed to be going nowhere. Donald Rumsfeld's attempts to sharpen defence policies had merely brought him into conflict with pen-pushing, risk-averse generals and their pork-barrelling allies in Congress. Over at the State Department and the National Security Council, meanwhile, all the intellectual talent appeared to be devoted to care and maintenance.

Mr Bush had no background in foreign affairs and had seen his father lose an election, despite the triumphs of the Gulf War, because he had neglected the home front. George Bush Jnr was also contemptuous of the way in which Bill Clinton had used foreign affairs to distract attention from dry-cleaning bills. The President was determined to avoid futile, grand-standing gestures. Although he might have assembled a strong foreign affairs team, he himself was still concentrating on domestic issues. It was not clear whether this Bush administration would have much of a foreign policy.

After 11 September, that was no longer an option. Al-Qa'ida had forced Mr Bush's hands while eliminating isolationism from the American political agenda. The bombers compelled Americans to recognise the new defining paradox: that the US was both immensely powerful and immensely vulnerable. Americans knew that they faced a global threat. But they also had the reassurance of knowing that their military possessed a global reach.

Post-11 September, grief was quickly transmuted into resolve. America prepared to fight back, and part of that preparation was hard thinking about the future of US foreign policy, an exhilarating process which is by no means complete and which will have radical outcomes. Suppose, however, that there had been no 11 September: that Bin Laden had decided to wait for a more propitious moment. He could easily have found one.

With every passing year, the risk of al-Qa'ida acquiring weapons of mass destruction would have been greater and, even if that danger had been avoided, Iraq would have posed a grave threat. It should not have taken 11 September to quicken American unease about Saddam into a campaign for his removal, but it did.

No 11 September, and there could have been a number of hideous outcomes, including an Israel/Iraq war, with both sides using weapons of mass destruction. The brutality of 11 September made Americans aware that they faced multiple risks. As those risks could so easily have involved the deaths of many more than 3,000 people and the destruction of much more than the buildings of Ground Zero, 3,000 lives was a cheap price to pay for an early warning. America had the shock it needed.

This is not a simple task, nor is it possible to guarantee success. There is no easy way to fight asymmetrical warfare, in which opponents with a minute fraction of America's strength are still able to inflict hideous damage. In the short run, we shall have to see whether we can get through this anniversary week without a major terrorist onslaught. (If we do, there are grounds for modest optimism. A successful outcome would suggest that al-Qa'ida's fangs have been drawn.)

The Americans know what they have to do. They can no longer tolerate rogue states which try to acquire weapons of mass destruction while providing terrorists with safe havens. Nor can the US tolerate failed states, which merely become enclaves of anarchy and whose perpetually disaffected populations provide endless foot soldiers for the recruiting sergeants of terrorism. America is beginning to realise that in order to eliminate the threat to itself, it has to clean up the globe.

This is among the best news that the world's poor have ever had, for in order to make the world safe for Americans it will be necessary to ensure that the wretched of the earth can enjoy some of the benefits which Americans take for granted. Though it would be easy to parody all this as a mission to evangelise on behalf of Coca-Cola and McDonald's, much more is involved. The US has always believed that societies which enjoy the benefits of democracy, the rule of law and the free market will tend to live at peace with their neighbours, breed relatively contented populations and maintain internal security within their own boundaries.

Sometimes this simple faith can lead to naive outcomes, as in Vietnam. In Henry Kissinger's words: "The United States had entered Indochina for highly moral reasons: the conviction that democratic institutions, being universally applicable, could be transplanted successfully to half of a divided country 8,000 miles away in the midst of a murderous civil war and that the principles that had restored Europe would prove equally applicable to the fledgling politics of South-east Asia.''

But occasional excesses do not invalidate either the principle or the generosity which lies behind it. Most Americans believe that over the past two and a half centuries, they have learned to make a human society work almost as well as is possible, within the constraints of original sin. They now feel that it is time for the Third World to profit by their example. That is a daunting exercise; then again, the Americans have never lacked optimism.

This is a week to mourn last year's victims, but the Bush administration knows that mourning is not enough. It is determined to take the necessary steps to ensure that there will be no second 11 September. If this proves successful, those who are still grieving will have one consolation. Last year's victims will not have died in vain.