This Sunday's NYT magazine carries a feature on the muddled intelligence in the runup to the Iraq war. Although formally there is nothing earth-shattering here, this is the first piece that offers a detailed timeline of how discredited intelligence came to be repeatedly peddled by high-ranking members of the administration:

...the [CIA's] first reports on the tubes [acquired by Iraq], which went to senior members of the Bush administration on April 10, 2001. The tubes, the report asserted, "have little use other than for a uranium enrichment program."

This alarming assessment was immediately challenged by the Energy Department, which builds centrifuges and runs the government's nuclear weapons complex.

The next day, Energy Department officials ticked off a long list of reasons why the tubes did not appear well suited for centrifuges. Simply put, the analysis concluded that the tubes were the wrong size - too narrow, too heavy, too long - to be of much practical use in a centrifuge...But if the tubes were not for a centrifuge, what were they for?

Within weeks, the Energy Department experts had an answer.

It turned out, they reported, that Iraq had for years used high-strength aluminum tubes to make combustion chambers for slim rockets fired from launcher pods. Back in 1996, inspectors from the International Atomic Energy Agency had even examined some of these tubes, also made of 7075-T6 aluminum, at a military complex, the Nasser metal fabrication plant in Baghdad, where the Iraqis acknowledged making rockets. According to the international agency, the rocket tubes, some 66,000 of them, were 900 millimeters in length, with a diameter of 81 millimeters and walls 3.3 millimeters thick.

The tubes now sought by Iraq had precisely the same dimensions - a perfect match...

Despite the ongoing debate in the intelligence community over the tubes - with, incidentally, most of the experts concurring with the assesment of the Department of the Energy that the tubes were not likely to be used for centrifuges - members of the administration presented the case with certainty:

Mr. Cheney, who has a history of criticizing officials who disclose classified information, typically refuses to comment when asked about secret intelligence. Yet on this day, with a Gallup poll showing that 58 percent of Americans did not believe President Bush had done enough to explain why the United States should act against Iraq, Mr. Cheney spoke openly about one of the closest held secrets regarding Iraq. Not only did Mr. Cheney draw attention to the tubes; he did so with a certitude that could not be found in even the C.I.A.'s assessments. On "Meet the Press," Mr. Cheney said he knew "for sure" and "in fact" and "with absolute certainty" that Mr. Hussein was buying equipment to build a nuclear weapon.

"He has reconstituted his nuclear program," Mr. Cheney said flatly.

Meanwhile, as the UN inspectors went into Iraq, it became possible to gather more evidence:

At the end of 2002, with the resumption of United Nations arms inspections, it became possible to seek answers inside Iraq. Inspectors from the International Atomic Energy Agency immediately zeroed in on the tubes.

The team quickly arranged a field trip to the Nasser metal fabrication factory, where they found 13,000 completed rockets, all produced from 7075-T6 aluminum tubes. The Iraqi rocket engineers explained that they had been shopping for more tubes because their supply was running low.

Why order tubes with such tight tolerances? An Iraqi engineer said they wanted to improve the rocket's accuracy without making major design changes. Design documents and procurement records confirmed his account.

The inspectors solved another mystery. The tubes intercepted in Jordan had been anodized, given a protective coating. The Iraqis had a simple explanation: they wanted the new tubes protected from the elements. Sure enough, the inspectors found that many thousands of the older tubes, which had no special coating, were corroded because they had been stored outside.

The inspectors found no trace of a clandestine centrifuge program.

Despite this, members of the administration continued to argue for the discredited theory and misrepresent the consensus of the experts. Cheney was not alone in this; apart from Condoleeza Rice's similar statement on Meet the Press, Colin Powell also made the same case before the UN:

Mr. Powell made claims that his own intelligence experts had told him were not accurate. Mr. Powell, for example, asserted to the Security Council that the tubes were manufactured to a tolerance "that far exceeds U.S. requirements for comparable rockets."

Yet in a memo written two days earlier, Mr. Powell's intelligence experts had specifically cautioned him about those very same words. "In fact," they explained, "the most comparable U.S. system is a tactical rocket - the U.S. Mark 66 air-launched 70-millimeter rocket - that uses the same, high-grade (7075-T6) aluminum, and that has specifications with similar tolerances."