It is one of the unanswered questions of the war: where are the weapons of mass destruction which both the United States and Britain said that Iraq possessed?
Because they have not been found does not mean they do not exist. They could have been hidden or destroyed.
The job of tracking down banned weapons is daunting
Judgment therefore has to be withheld.
The US military commander, General Tommy Franks, says that it could take a year to complete a search.
But if they are not found there will be recriminations. The war was justified on the grounds that Iraq had not complied with UN resolutions to declare and destroy them.
Jon B. Wolfsthal, a weapons expert at the Carnegie Endowment for International Peace in Washington said: "Failure to discover chemical and biological weapons in Iraq will be used by many groups to vilify the United States".
"It will also reinforce claims that such weapons were only a pretext for America to remove Saddam's regime for other political or geostrategic reasons," he added.
The chief UN weapons inspector, Hans Blix, remains open-minded about whether Iraq had such weapons, but is highly critical of Britain and the US. He accused them of planning the war "well in advance" and of "fabricating" evidence against Iraq.
Certainly, the dossiers issued by both the CIA and the UK Government before the war proved very weak in crucial aspects.
One of the most damaging claims, for example, that Iraq had sought to acquire uranium from an African country, was disproved by the International Atomic Energy Agency. It discovered that documents on which the claim had been made were crude forgeries.
The IAEA came close to saying that Iraq had no nuclear weapons programme.
Several of the plants named in the dossiers as potential places for chemical and biological warfare manufacture were inspected by the UN teams and found not to be incriminating.
None of the 12 to 20 Scud missiles Iraq was accused of retaining have been found.
Elusive mobile labs
Nor have the so-called mobile biological warfare laboratories, about which a great deal was made. Drawings of these were presented to the Security Council by US Secretary of State Colin Powell.
I was knowledgeable about these programmes. I was telling the truth, always telling the truth
General Amer al-Saadi
Top Iraqi scientific adviser
Some were reminded of the plot of the Graham Greene novel Our Man In Havana, in which a British agent based his descriptions of secret installations on the vacuum cleaners he sold in his shop.
On the other hand, Mr Powell did provide evidence, from intercepted phone calls, that some material was being hidden by the Iraqis - what were called "special vehicles" among them.
Rumours and false leads
There have been numerous rumours and false leads. There was the case of the US soldiers who were overcome by the "effects of a nerve agent" near Karbala. It turned out that they had been suffering from dehydration and recovered quickly after food and drink. The suspect chemicals proved to be pesticides.
The latest report concerns some buried containers, which, it is said, could be the elusive mobile laboratories.
US/UK team in Iraq
So the United States and Britain have started to look for evidence on the ground.
They are currently unwilling to let the UN do the job.
Already an 80-strong US/UK team is in the port of Umm Qasr. They are looking through thousands of pages of customs documents, seeking signs that illegal material was imported.
The BBC programme Newsnight was allowed to film them at work, blowing up safes to get at documents, scanning them and e-mailing the results back to Washington for analysis.
Scientists - a key source
The best source of information is likely to be, as was said all along, the Iraqi scientists.
One of them, General Amer al-Saadi, Saddam Hussein's senior scientific adviser, surrendered to US troops after the fall of Baghdad. He became well known as the well-spoken media spokesman who denied that Iraq had tried to rebuild its weapons of mass destruction.
But he said during his surrender, which he organised through a German television crew from ZDF, that he had not been lying.
"I was knowledgeable about these programmes. I was telling the truth, always telling the truth," he said.
Was Iraq a threat?
There are other issues as well. It was part of the American and British case that Iraq posed a real threat because it could provide weapons of mass destruction to international terrorists.
If no such weapons are found, that claim will be undermined.
No doubt, Washington and London could construct a defence. They could say that Iraq had the capacity to make such weapons and that therefore the threat did exist.
But they would be on the defensive and their statements about the programmes of other countries - such as Syria, North Korea, Iran and Libya, would not be readily believed.
It is important for both governments that their claims are substantiated.