Before the war he told us that Saddam had “large stockpiles of chemical and biological weapons and an active program to develop nuclear weapons”. After the war he explains away the failure to find any of these stockpiles or nuclear installations on the possibility that Saddam’s regime “decided they would destroy them prior to a conflict’’. You have to admire his effrontery.

But not his logic. The least plausible explanation is that Saddam destroyed his means of defense on the eve of an invasion. The more plausible explanation is that he did not have any large stockpiles of weapons of mass destruction.

We need to rescue the meaning of words from becoming a further casualty of the Iraqi war. A weapon of mass destruction in normal speech is a device capable of being delivered over a long distanse and exterminating a strategic target such as a capital city. Saddam had neither a long-range missile system nor a warhead capable of mass destruction.

Laboratory stocks of biological toxins or chemical shells for use on the battlefield do not add up to weapons of mass destruction. But we have not yet found even any of these.

When the British Cabinet discussed the dossier on Saddam’s weapons of mass destruction I argued that I found the document curiously “derivative’’. It set out what we knew about Saddam’s chemical and biological arsenal at the time of the (previous) Gulf War. It rehearsed our inability to discover what had happened to those weapons. It then leapt to the conclusion that Saddam must still possess all those weapons. There was no hard intelligence of a current weapons program that would represent a new and compelling threat to our interests.

Nor did the dossier at any stage admit the basic scientific fact that biological and chemical agents have a finite shelf life. Odd, since it is a principle understood by every chemist. Go in to your medicine cupboard and check out the existence of an expiry date on nearly everything you possess.

Nerve agents of good quality have a shelf life of about five years and anthrax in liquid solution of about three years. Saddam’s stocks were not of good quality. The Pentagon itself concluded that Iraqi chemical munitions were of such poor standard that they were produced to a “make-and-use’’ regime under which they were usable for only a few weeks. Even if Saddam had destroyed none of his arsenal from 1991 it would long ago have become useless.

It is inconceivable that no one in the Pentagon told Donald Rumsfeld these home truths, or at the very least tried to tell him. So why did he build a case for war on a false claim of Saddam’s capability?

Enter stage right (far right) his deputy, Paul Wolfowitz, a man of such ferociously reactionary opinion that he has at least the advantage to his department of making Rumsfeld appear reasonable. He has now disclosed: “For bureaucratic reasons we settled on weapons of mass destruction because it was the one issue everyone could agree on.’’

Wolfowitz is famously a regime-change champion. He was one of the flock of Republican hawks who wanted a war to take over Iraq long before Sept. 11. Decoded, what his remarks mean is that the Pentagon went along with allegations of weapons of mass destruction as the price of getting Secretary of State Colin Powell and the British government on board for war. But the Pentagon probably did not believe in the case then and certainly cannot prove it now.

Wolfowitz also let the cat out of the bag over the “huge prize” for the Pentagon from the invasion of Iraq. It has furnished them with an alternative to Saudi Arabia as a base for US influence in the region.

As Donald Rumsfeld might express it, we have been suckered. Britain was conned into a war to disarm a phantom threat in which not even our major ally really believed. The truth is that the US chose to attack Iraq not because it posed a threat, but because they knew it was weak and expected its military to collapse. It is a truth that leaves the British government in an uncomfortable position. This week Prime Minister Tony Blair was pleading for everyone to show patience and to wait for weapons to be found. There is an historic problem with this plea. The war only took place because the coalition powers lost patience with Hans Blix and refused his plea for a few more months to complete his disarmament tasks.

There is also a growing problem of trans-Atlantic politics with the British prime minister’s plea for more time. The US administration wanted the war to achieve regime change and now they have got it they do not see why they need to keep up the pretence that they fought it to deliver disarmament. The more time passes, the greater the gulf will widen between the obliging candor on the US side that there never was a weapons threat and the desperate obfuscation on the British side that we might still find one.

There is always a bigger problem in denying reality than in admitting the truth. The time has come when the British government needs to concede that we did not go to war because Saddam was a threat to our national interests. We went to war for reasons of US foreign policy and Republican domestic politics.

One advantage of such clarity is that it would help prevent us from being suckered a second time. Which brings us to Rumsfeld’s latest sabre-rattling against Iran. It is consistent with the one-dimensional character of the Rumsfeld world view. This time we must make clear to the White House that we are not going to subordinate Britain’s interests to a US policy of confrontation. Iran must not become the next Iraq.