Rupert Cornwell: Unlike Vietnam, this is a war that the Americans are thirsting to fight

The horror of 11 September has put an end to many things in America, among them the country's aversion to wars in which American soldiers die. Methods of warfare are, to a large extent, dictated by what the public will tolerate.

The horror of 11 September has put an end to many things in America, among them the country's aversion to wars in which American soldiers die. Methods of warfare are, to a large extent, dictated by what the public will tolerate.

America's recent obsession with hi-tech "virtual reality" combat came to full fruition in Kosovo, fought with high-altitude bombs and guided missiles, where the front line for America was a virtually impregnable 15,000 feet in the sky above the Balkans. But, as the civilian death count from the atrocities runs into the thousands, so the squeamishness has vanished about sacrificing men whose voluntary profession is to fight for the US and die for that cause if required.

It has long been otherwise. The key, of course, was Vietnam, exemplar of military futility when 58,000 American lives were lost in a war halfway around the world, that could not be won except by methods that would defeat the ends, and whose very nature – nationalist not ideological – the US could not understand. The experienced changed many minds, including that of a young lieutenant named Colin Powell who would rise to become a formulator of US military policy.

Wars when Powell was the National Security Adviser and then the Chairman of the Joint Chiefs of Staff, had to be short, clear-cut, and conclusively winnable. In them, maximum force was brought to bear against the enemy, swiftly breaking its will and minimising the danger to his own men in arms. The Gulf War, in which 500,000 US troops were dispatched 6,000 miles to drive Saddam Hussein from Kuwait, was the apotheosis of this doctrine – a logistical and strategic triumph in which the fighting on the ground lasted only 100 hours, and American losses were fewer than 150. But the Gulf War did not entirely banish the demons of Vietnam.

Hardly had Bill Clinton entered the White House than dreadful pictures of US peacekeepers being dragged by Somali mobs through the streets of Mogadishu appeared on US screens. Straightforward war fought under conditions in which America could not lose, again became the watchword.

Then came the Balkans, and the celebrated Powell aphorism summing up the Pentagon's aversion to open-ended commitments: "We do deserts, not mountains." The Dayton agreement spared that resolve from being put to the test, but Kosovo was new vindication of it. In this conflict, no American soldier saw his opponent in the flesh; the American public preferred it that way.

No longer. The current mood may be summed up in three words: Get the bastards. Not just in the lust for vengeance shared by editorial columns and commentators, but by luminaries such as Lawrence Eagleburger the former Secretary of State. "There is only one way to deal with people like this. You have to kill some of them even if they are not immediately involved in this thing." This is gut patriotism, the sort of patriotism that propelled the sales of US flags at Wal-Mart stores on Wednesday to 88,000. This patriotism says America must respond and if more American blood must be spilt to achieve that end then so be it. If New York City has requested 6,000 bodybags, the Pentagon must make ready some of its own.

Bill Clinton responded to the previous terrorist attack on the US with cruise missile salvos against Aghanistan and Sudan. They achieved nothing. If Osama bin Laden indeed proves to be the mastermind behind the carnage, missiles will not be enough.

This time, it will not require a Desert Shield or Desert Storm, and half a million men. If the US decides to wipe out Mr bin Laden, his cells and training camps, it will take far fewer. It may take the support of the Apache helicopters that the Pentagon refused to risk in Kosovo. It will certainly take men on the ground, some of whom will doubtless be killed.

Even this strategy will not eradicate the terrorist threat. America will have responded to an act of war with an act of war of its own – which prompts yet another act of war, perhaps with weapons even deadlier than kerosene-packed civilian jetliners. It will be a multifront war, on awkward terrain with no exit strategy In those respects, just like Vietnam. But this time it is a war the US is thirsting to fight.