Did the weapons not exist, as some have suggested? Or were they destroyed before the war, as others believe?

In a VOA interview, former U.S. chief weapons inspector David Kay, who led the hunt for Iraq's weapons, says there is no evidence they ever existed. "I personally don't think there's a chance to find them, because the evidence that they were not produced is compelling. And, so, if they weren't produced, there's nothing to be found. Is it appropriate to continue looking? Yes, I think it is appropriate to continue to look," he said.

But if the weapons did not exist, why did Saddam Hussein let the world believe he had them, a stance, which plunged his country into war and occupation and led to his own downfall and capture? It is a key question that confounds experts.

Richard Perle, former assistant secretary of defense for international security affairs and a Bush administration advisor, disagrees with the idea the weapons were nonexistent. Speaking by telephone, Mr. Perle says Saddam Hussein did have chemical and biological weapons, at least in the time leading up to the war.

"We do know that these things were produced. And we know that Saddam was asked to explain what happened to them, and he refused to do so," he said. "If you had to make a judgment at the time under conditions of uncertainty, the only reasonable judgment to make was that things he could not account for, he could not account for, because he had hidden them away. And he couldn't admit to that. So, it was the assumption made by virtually all the world's intelligence organizations."

The other key question is how intelligence agencies, not only in the United States, but in Britain and elsewhere, got it so wrong. Mr. Perle agrees that it was a major, but still unexplained, intelligence failure.

"There's no question that it was an intelligence failure, no question at all," he said. "The intelligence community believed it had a lot of information, both inventory information and a great deal of circumstantial evidence about the movement and hiding of things, and it turns out things were not where they expected them to be."

David Kay, the former weapons inspector, says he does not believe intelligence was deliberately distorted, as some opponents of the administration have alleged. He says that, after the U.N. inspectors left Iraq in 1998, intelligence agencies found their sources of information to be greatly reduced.

"Then, after '98, we tended to rely very much more on defectors, refugees that were organized by one or the other of the émigré organizations, and had their own political agendas, which involved getting rid of Saddam," he said. "And so, they told us stories about WMD. The stories just didn't happen to be true."

Critics have charged that the intelligence was politicized by an administration already determined to oust Saddam Hussein. Joseph Nye, also a former assistant secretary of defense for International Security Affairs and now dean of the Kennedy School of Government at Harvard University, says the administration selectively picked intelligence to bolster its case.

"I think it was an intelligence failure. And also, there was a great deal of political exaggeration by politicians, who sort of picked the intelligence that supported their view, and that was also true, not just in the United States, but in Britain and other countries," he said.

That brings a forceful denial from Richard Perle. "One thing is absolutely certain: There was no effort to deceive people about our intelligence judgments," he said. "We went to enormous lengths to prepare our troops in the field to confront chemical weapons, for example. That was not a charade, that was not a show. It flowed from the conviction that he [Saddam] had quantities of these weapons."