The present world situation is unprecedented. The great global empires of the past--such as the Spanish and notably the British--bear little comparison with what we see today in the United States empire. A key novelty of the US imperial project is that all other empires knew that they were not the only ones, and none aimed at global domination. None believed themselves invulnerable, even if they believed themselves to be central to the world--as China did, or the Roman empire. Regional domination was the maximum danger envisaged until the end of the cold war. A global reach, which became possible after 1492, should not be confused with global domination.

The British empire was the only one that really was global in a sense that it operated across the entire planet. But the differences are stark. The British empire at its peak administered one quarter of the globe's surface. The US has never actually practised colonialism, except briefly at the beginning of the 20th century. It operated instead with dependent and satellite states and developed a policy of armed intervention in these.

The British empire had a British, not a universal, purpose, although naturally its propagandists also found more altruistic motives. So the abolition of the slave trade was used to justify British naval power, as human rights today are often used to justify US military power. On the other hand the US, like revolutionary France and revolutionary Russia, is a great power based on a universalist revolution--and therefore on the belief that the rest of the world should follow its example, or even that it should help liberate the rest of the world. Few things are more dangerous than empires pursuing their own interest in the belief that they are doing humanity a favour.

The cold war turned the US into the hegemon of the western world. However, this was as the head of an alliance. In a way, Europe then recognised the logic of a US world empire, whereas today the US government is reacting to the fact that the US empire and its goals are no longer genuinely accepted. In fact the present US policy is more unpopular than the policy of any other US government has ever been, and probably than that of any other great power has ever been.

The collapse of the Soviet Union left the US as the only superpower. The sudden emergence of a ruthless, antagonistic flaunting of US power is hard to understand, all the more so since it fits neither with long-tested imperial policies nor the interests of the US economy. But patently a public assertion of global supremacy by military force is what is in the minds of the people at present dominating policymaking in Washington.

Is it likely to be successful? The world is too complicated for any single state to dominate it. And with the exception of its superiority in hi-tech weaponry, the US is relying on diminishing assets. Its economy forms a diminishing share of the global economy, vulnerable in the short as well as long term. The US empire is beyond competition on the military side. That does not mean that it will be absolutely decisive, just because it is decisive in localised wars.

Of course the Americans theoretically do not aim to occupy the whole world. What they aim to do is to go to war, leave friendly governments behind them and go home again. This will not work. In military terms, the Iraq war was successful. But it neglected the necessities of running the country, maintaining it, as the British did in the classic colonial model of India. The belief that the US does not need genuine allies among other states or genuine popular support in the countries its military can now conquer (but not effectively administer) is fantasy.

Iraq was a country that had been defeated by the Americans and refused to lie down. It happened to have oil, but the war was really an exercise in showing international power. The emptiness of administration policy is clear from the way the aims have been put forward in public relations terms. Phrases like "axis of evil" or "the road map" are not policy statements, but merely soundbites. Officials such as Richard Perle and Paul Wolfowitz talk like Rambo in public, as in private. All that counts is the overwhelming power of the US. In real terms they mean that the US can invade anybody small enough and where they can win quickly enough. The consequences of this for the US are going to be very dangerous.

Domestically, the real danger for a country that aims at world control is militarisation. Internationally, the danger is the destabilising of the world. The Middle East is far more unstable now than it was five years ago. US policy weakens all the alternative arrangements, formal and informal, for keeping order. In Europe it has wrecked NATO--not much of a loss, but trying to turn it into a world military police force for the US is a travesty. It has deliberately sabotaged the EU, and also aims at ruining another of the great world achievements since 1945: prosperous democratic social welfare states. The crisis over the United Nations is less of a drama than it appears since the UN has never been able to do more than operate marginally because of its dependence on the security council and the US veto.

How is the world to confront--contain--the US? Some people, believing that they have not the power to confront the US, prefer to join it. More dangerous are those who hate the ideology behind the Pentagon, but support the US project on the grounds that it will eliminate some local and regional injustices. This may be called an imperialism of human rights. It has been encouraged by the failure of Europe in the Balkans in the 1990s. The division of opinion over the Iraq war showed there to be a minority of influential intellectuals who were prepared to back US intervention because they believed it necessary to have a force for ordering the world's ills. There is a genuine case to be made that there are governments so bad that their disappearance will be a net gain for the world. But this can never justify the danger of creating a world power that is not interested in a world it does not understand, but is capable of intervening decisively with armed force whenever anybody does anything that Washington does not like.

How long the present superiority of the Americans lasts is impossible to say. The only thing of which we can be absolutely certain is that historically it will be a temporary phenomenon, as all other empires have been. In the course of a lifetime we have seen the end of all the colonial empires, the end of the so-called thousand-year empire of the Germans, which lasted a mere 12 years, the end of the Soviet Union's dream of world revolution.

There are internal reasons, the most immediate being that most Americans are not interested in running the world. What they are interested in is what happens to them in the US. The weakness of the US economy is such that at some stage both the US government and electors will decide that it is much more important to concentrate on the economy than to carry on with foreign military adventures. Even by local business standards Bush does not have an adequate economic policy for the US. And Bush's existing international policy is not a particularly rational one for US imperial interests--and certainly not for the interests of US capitalism. Hence the divisions of opinion within the US government.

The key questions now are: what will the Americans do next, and how will other countries react? Will some countries, like Britain, back anything the US plans? Their governments must indicate that there are limits. The most positive contribution has been made by the Turks, simply by saying there are things they are not prepared to do, even though they know it would pay. But the major preoccupation is that of--if not containing--educating or re-educating the US. There was a time when the US empire recognised limitations, or at least the desirability of behaving as though it had limitations. This was largely because the US was afraid of somebody else: the Soviet Union. In the absence of this kind of fear, enlightened self-interest and education have to take over