It was the moment that summed up the strange, self-denying character of the new American empire. As the blitzkrieg against Saddam Hussein reached its climax in Baghdad last week, an American marine clambered atop the statue of Saddam Hussein in Paradise Square and draped the stars and stripes over its head.

But within minutes — obviously in response to a frantic order from his superiors — the soldier was sheepishly replacing the American flag with an old Iraqi flag.

He had gone spectacularly off-message. He had forgotten that this was a victory, not for the US but for the Iraqi people. As The New York Times declared sanctimoniously the next morning, the key thing was to make this a “war of liberation” not a “war of conquest”.

So let’s be clear. Conquest is liberty. Defeat is victory. And that retired American general who is just about to take over the country is — no, not governor-general, not viceroy — he is chief executive officer for reconstruction and humanitarian assistance.

Welcome to the weird and wonderful world of the Pax Americana — the empire that dare not speak its name.

To a Briton living in the United States, it can be rather baffling. As I write, the only authority in Iraq is that of the American and British military. Already American and British firms are queueing up to reconstruct the Iraqi economy, not least its bountiful oil fields. If this isn’t imperialism, what is? On March 11, 1917 British troops captured Baghdad, signalling the beginning of the end for the Turkish empire in the Middle East. It was a decisive moment in a now largely forgotten desert storm. Unlike the Americans the British felt no compunction about unfurling their national flag to mark their victory. In fact, it was not until 1932 that power was formally handed over to the new monarchy — and even then the British continued to run Iraq behind the scenes until the revolution of 1958.

Whereas Britain tended to regard the language of liberation and democracy as so much cant — to put an acceptable face on the reality of conquest — Americans today seem genuinely to mean it. Even hawks like Paul Wolfowitz, the deputy defence secretary, apparently agree that this is a war to democratise, not dominate, Iraq.Wolfowitz assured reporters last weekend that the Pentagon intended to install nothing more than an interim administration in Iraq. The time-frames being talked about in Washington for a transition to Iraqi self-government range from six to 24 months.

Britain’s imperial experience suggests this is wildly unrealistic. If Iraq was still not ready for democracy after 40 years of British rule a mere two years of American rule is unlikely to do the trick. The post-war occupation will need to last 10 years at least.

Bush likes to compare what he is attempting in Iraq to what his predecessor, Harry Truman, did in post-war Germany and Japan. “America has made and kept this kind of commitment before,” he argued in February. “After defeating enemies we did not leave behind occupying armies, we left constitutions and parliaments.”

This would be nice if it were true. In fact, the formal military occupation of Japan did not end until 1952 and that of West Germany not until 1955, making a total military occupation of, respectively, seven and 10 years. And the biggest overseas concentrations of American troops in the world even today are in, yes, Germany (69,000) and Japan (40,000).

By comparison some of the biggest failures of recent US foreign policy — Somalia (1993) and Haiti (1994) — have been the result of precisely the short-termism in evidence in Washington today. In both cases American troops were deployed for far too short a period to achieve anything of value. Both countries are in as big a mess today as they were before the US intervened. If Bush leaves Iraq prematurely it will be the same story.

In scrupulously avoiding anything that might be construed as imperialistic the administration is, of course, doing nothing more than reflecting the mood at home. Americans have it drummed into them from kindergarten that their political lexicon doesn’t include the “E” word. The US was forged in a revolt against British colonialism (see The Patriot). It has only fought wars to free oppressed peoples (see Band of Brothers).

Even hardnosed conservatives share this allergy to empire. Early in 2001 I tried to persuade the members of the libertarian Cato think tank in Washington that the US had a duty to overthrow rogue regimes like Saddam Hussein’s. They looked at me as if I were mad.

Times Recommends

• Michael Jackson: Not the final chapter
• Indian Army spends10m rupees on golf buggies
• Brüno toned down for 15 rating