For a decade, democracies have progressively fallen prey to the illusion that threats from abroad have disappeared, that dangers, if any, were primarily psychological or sociological in origin, that, in a sense, history itself as previously recorded has been transformed into a subdivision of economics or psychiatry.

Although America had experienced terrorism, it was generally aimed at US installations abroad; the impact was largely symbolic and stopped well short of threatening lives and civil society in the US.

The response has usually been condemnation, one or two retaliatory raids, and criminal prosecution of such perpetrators as could be found. The current situation dictates a new approach. President George W. Bush wisely has warned that the attacks on New York and Washington amounted to a declaration of war. And in a war it is not enough to endure; it is essential to prevail.

The attacks represent a fundamental challenge to US civil society and security. The target was not America's military but the morale and way of life of the civilian population.

Above all, the disaster brings home that some of the comfortable premises of the globalised world do not apply to that portion of it that resorts to terrorism. That segment seems motivated by a hatred of Western values so deep that its representatives are prepared to face death and inflict vast suffering on innocents, threatening the destruction of our societies on behalf of what is conceived as a clash of civilisations.

As these realities penetrate the consciousness of the democratic world, the terrorists have already lost an important battle. In the US, they will face a united people determined to eradicate the evil of terrorism at any cost. In the Western alliance, they have ended the debate about whether there is still a common purpose in the post-Cold War world.

All Western democracies have recognised that the assault on America - if unpunished - is a prelude to what can happen even more easily to their own societies.

The shared experiences of nearly two generations have not been forgotten, after all, and remain relevant.

But other nations outside the NATO framework share as well a common interest not to be subject to blackmail by shadowy terrorist groups using their capacity to inflict suffering for a strategy based on inhumanity and not accountable to any institutional restraints.

The challenge, then, becomes how to translate the common purposes into operational policy.

As far as the US is concerned, there should be an initial sweeping review of intelligence procedures and organisation.

To what extent has the belief in a period of relative tranquillity encouraged a certain lassitude about expectations? To what extent have limitations on resources played a role? Is a new organisation needed to accommodate countermeasures?

Next, retaliatory blows against the perceived resources of this attack are necessary. Half measures are more likely to do harm than good.

The most important task, however, is to go beyond retaliation to rooting out the core of terrorism. The war, President Bush has affirmed, must be won, not conducted as a tit-for-tat of exchanging blows. It is therefore imperative to move beyond the existing pattern of retaliation and criminal prosecution to taking the fight to the source of the problem.

The terrorist organisations must be put on the defensive, their networks broken up, their source of funds cut off and, above all, their home bases put under unrelenting pressure to deny them safe havens. Prevent further carnage by getting the terrorist groups on the run, and then destroy them.

It is surely not beyond the scope of the intelligence services of the democracies to identify organisations capable of such global efforts. The number of countries that shelter them is finite enough.

The immediate challenge is to put these countries on notice that they will be outcasts if they continue to extend asylum; that the US will feel free to attack militarily installations that threaten the security of free peoples; that the US holds the countries supplying havens specifically responsible for attacks launched by organisations with which they have cooperated. Specifically:

The US should demand the extradition from Afghanistan of Osama bin Laden or his expulsion from Afghan territory. Whether his group has been involved in the attacks on New York and Washington, he has been implicated in other attacks on American property and lives. If Afghanistan refuses, the US should feel free to attack bin Laden's installations or any Afghan installations capable of supporting him. If he is expelled, any government that gives him shelter should be informed of America's determination to take military measures in pursuit of him, against his organisation and the supporting facilities of the host country.

A list of terrorist groups should be published. Governments should be warned that any country affording them havens will face a complete, strictly enforced, economic boycott; a denial of US (and hopefully allied) visas to its citizens; a denial of US financial facilities to its citizens; the risk of military measures against the terrorist headquarters and supporting host country facilities. All countries should be warned that encouragement of terrorism by state-supported media will be treated as an unfriendly act.

America and its allies must take care not to present this new policy as a clash of civilisations between the West and Islam. The battle is against a radical minority that disgraces the humane aspects Islam has displayed in its great periods.

Then there is the argument that America should modify its foreign policy to remove the resentments that produce terrorism.

Of course US policy should be under constant review. And good relations with the Islamic nations must be a principal component.

However, moderation is a virtue only in those known to have an alternative. It is not in the interest of even the moderate Islamic nations that US - or Western - policy is perceived as cowering before the threat or actuality of terror. The first victims of such a course would be the moderates in the Islamic world and, in the long run, all the populations of the democracies.

Having overcome the vast military and ideological threats of the past half a century, we must now master this more indirect but perhaps even more insidious peril and turn it into an equally decisive victory.

Henry Kissinger was US secretary of state in the Nixon and Ford administrations. This article first appeared in the Los Angeles Times.