"Trust us" is a hard line to swallow, for Americans as well as Britons. After all, Americans, too, note that we are close the anniversary of the attack on Iraq and that weapons of mass destruction remain unrecovered. As for Guantanamo Bay, for a while it seemed that the Pentagon wanted to keep many detainees for ever, or at least indefinitely.

Guantanamo especially has been difficult to take. One of the bonuses of taking prisoners in old-fashioned war is the chance to redeem ourselves by acting magnanimously towards the captives. The Pentagon seemed to be depriving everyone of that chance with its tough behaviour at the naval base.

Still, when you examine them closely, the US administration's fatiguing campaigns and unsettling actions begin to make sense. The war on terrorism, the administration posits, is not an old-fashioned war but a new kind of war in which the Pentagon too is feeling its way. The US would love to be magnanimous. But magnanimity comes when the war is over. And it is not over: as recently as last month, Taliban bombs killed UK and Canadian soldiers in Afghanistan. Al-Qaeda has not given up and Osama bin Laden's spider hole has not been found.

In recent days the administration has put forward some arguments and details about Guantanamo to show where the naval base fits into this context. It has also announced a new process for prisoner review and possible release.

The administration's first point is that it is wrong to present Guantanamo as a human rights story. Guantanamo ought rather to be acknowledged for what it has turned out to be: a trove of intelligence - the sort of trove that can help us figure out how to end this tiring war.

The administration did not hand out a name-list. But it did share plenty of new facts about its charges. A number of detainees are high-ranking al-Qaeda leaders; some of them have said outright that they would plot future attacks if freed. Among the detainees is an explosives trainer who has provided information on the September 2001 assassination of Ahmed Shah Masood, the Afghanistan Northern Alliance leader. Other prisoners have worked on attacks including those on the US embassies in east Africa and the one on the USS Cole in Yemen.

At Guantanamo, there are detainees who have taken part in hijackings; there are some who have sworn personal allegiance to Osama bin Laden. One man has provided basic information about al-Qaeda front companies and banks; another has talked about his work as support for a cell that targeted journalists and aid workers. Others have said they would organise bombings if free. Finally, there are detainees who have helped bring al-Qaeda operatives into the US via Latin America.

Had the military "processed" these people as swiftly as human rights watchdogs demanded, it might never have collected so much information, the administration says. One detainee alone maintained 17 aliases. One of the surprises at Guantanamo has been the common use of a terrorism primer first discovered by the police in Manchester, England. The Manchester Manual, as it is known, contains a section on counter-intelligence that helps prisoners trick interrogators. Releases remain risky, the administration warns, and some former detainees have already rejoined the Taliban.

The administration's second point is that it has not mistreated prisoners. No prisoner has died. The same doctors who serve the military take care of the prisoners. And now new panels, something like parole boards, will review detainees. They will free some, keep some and transfer others to the custody of foreign governments - which it expects to guard them carefully. This is the principal tension between the US administration and David Blunkett, Britain's home secretary, who has indicated that detainees would be freed if the evidence against them would not stand up in a British court.

What about the injustice of "legal limbo"? In fact there is no legal limbo, the administration says. Because the war is not over, the US has the right to detain enemy combatants without trial or lawyers, just as governments in earlier conflicts did not provide such things. What is more, the combatants held are not prisoners of war under the Geneva Conventions and so are not entitled to POW privileges: they did not wear uniforms and they targeted civilians. They are different from, say, captured Iraqis, who are POWs and have been treated as such. Later, the US will prosecute some Guantanamo detainees as war criminals; they will then have the same privileges seen after the second world war.

These "trust us" arguments are so nuanced that they fit uneasily into our straightforward Anglo-American culture of fairness. But then, one of the aims of terrorists has always been to force us into such ambiguous corners. Terrorists turn societies against themselves. It is easier to blame the security guard checking your shoes than the original terrorist with the shoe bomb. The bunker mode becomes increasingly unbearable.

All of this takes us back to war fatigue. US foreign policy is here a casualty of its own success. Saddam Hussein's capture strengthens the temptation to declare victory and send everyone home. Still, to parole and liberate the Guantanamo detainees more rapidly than the Pentagon's new regime allows would be to assume that al-Qaeda has no more plans. In the end the choice remains simple and bitter. It is "trust us" - or trust them.

© Copyright 2004 Financial Times