"The president would like to make a change," Card said, using a time-honored formulation that avoided the words "resign" or "fire." He noted briskly that there had been some discussion of having Powell remain until after Iraqi elections scheduled for the end of January, but that the president had decided to take care of all Cabinet changes sooner rather than later. Bush wanted Powell's resignation letter dated two days hence, on Friday, November 12, Card said, although the White House expected him to stay at the State Department until his successor was confirmed by the Senate.

After four long years, Powell had anticipated the end of his service and sometimes even longed for it. He had never directly told the president but thought he had made clear to him during the summer of 2004 that he did not intend to stay into a second term.

There had been public speculation as the election drew near that the president might ask the secretary of state to reenlist, at least temporarily. Powell was still the most popular member of Bush's team, far more popular with the public than the president himself. Senior Powell aides were convinced that the secretary anticipated an invitation to stay, and they were equally certain that he intended to accept. The approaching elections in Iraq, hints of progress in the Israeli-Palestinian peace process and the rumored departure of Defense Secretary Donald Rumsfeld, a principal Powell nemesis, made the next six months look like a rare period of promise for diplomacy.

The president himself made no contact with Powell after Card's call. For two days, the only person at the State Department Powell told about it was his deputy and friend of decades, Richard Armitage. Powell dropped off his resignation letter, as instructed, after typing it himself on his home computer. (The White House later pointed out a typo and sent it back to be redone.) Loath to reveal either surprise or insult, he used the letter to claim the decision to leave as his own.

"Dear Mr. President:" he wrote. "As we have discussed in recent months, I believe that now that the election is over the time has come for me to step down as Secretary of State . . . effective at your pleasure."

He was pleased, Powell said, to "have been part of a team that launched the Global War Against Terror, liberated the Afghan and Iraqi people, brought the attention of the world to the problem of proliferation, reaffirmed our alliances, adjusted to the Post-Cold War World and undertook major initiatives to deal with the problem of poverty and disease in the developing world. In these and in so many other areas, your leadership was the driving force of our success."

AFTER HIS DEPARTURE FROM THE STATE DEPARTMENT IN JANUARY 2005, Powell traveled the lecture circuit, making paid speeches on leadership and U.S. foreign policy to corporate boards and industry conventions. He never spoke publicly about the specific circumstances of his resignation as secretary of state except to say, when asked, that Cabinet reshuffles were normal at the end of a four-year mandate, and that his departure had been a "mutual decision" between him and the president.

He artfully brushed aside inquiries about the many published accounts of deep ideological schisms that had rent Bush's national security team throughout the first term and the private humiliations he reportedly had endured at the hands of powerful colleagues.

Audiences often asked about his public role in promoting and defending what many now consider to be the most ill-advised act of Bush's presidency: the March 2003 invasion of Iraq. Powell usually offered a tepid defense, allowing only that he wished there had been more troops committed to the war and its aftermath, and a better plan to rebuild the country.

Powell had thrown his considerable personal and professional reputation behind the administration's charges that Iraq possessed chemical, biological and perhaps even nuclear weapons, and posed an imminent threat to the United States. In a crucial speech to the United Nations Security Council six weeks before the invasion was launched, he had single-handedly convinced many skeptical Americans that the threat posed by Iraqi dictator Saddam Hussein was real.

But the war had gone sour almost from the moment U.S. troops rolled triumphantly into Baghdad two months later. Powell's credibility had been seriously undermined when the weapons he cited as the main justification for invasion turned out not to exist.

No one in his legions of admirers wanted to believe that Powell had been duped by the White House -- or, worse yet, that he had knowingly betrayed the nation's trust. Many assumed that he had privately argued against such a clearly misguided adventure and been overruled.

In fact, Powell had never advised against the Iraq invasion, although he had warned Bush of the difficulties and counseled patience. He had no reason to resign over Iraq, he told questioners. But the larger mystery of his tenure as the nation's chief diplomat, fourth in line for succession to the presidency, remained.

When Bush selected Powell as his secretary of state in December 2000, it was seen as a stroke of political genius that instantly assuaged concerns at home and abroad about the president-elect's conspicuous lack of foreign policy experience. As national security adviser to one president and chairman of the Joint Chiefs of Staff under two more, Powell had helped guide the nation through the end of the Cold War and had brought the military to victory in the Persian Gulf War. By the time he retired from the Army as a four-star general in 1993, he was a national icon of wise leadership -- the "most trusted man in America," according to polls.

Yet Powell had constantly found himself on the losing side of regular ideological combat inside the Bush administration, particularly against Rumsfeld and the powerful vice president, Dick Cheney, over Iraq and a host of other foreign policy issues. Though Powell had scored some victories, the rumored humiliations had been real. He had been purposely cut out of major foreign policy decisions more than once, and his advice often had gone unheeded or been only grudgingly accepted by the president. Why hadn't he resigned?

The easy answer had the virtue of truth: Soldiers didn't quit when they disagreed with the decisions of their commanders. The fact that he had been out of uniform for nearly a decade was irrelevant to Powell; he would be a soldier until he drew his last breath.

AS TEXAS GOV. GEORGE W. BUSH BEGAN HIS CAMPAIGN FOR THE PRESIDENCY IN 1999, Powell's initial impression was that Bush was "still getting his sea legs" on foreign policy and national security issues. Powell knew "Sonny," as he referred to him, only in passing, and his private preference was for another Republican candidate: Arizona Sen. John McCain, a fellow military officer and Vietnam veteran.

But Powell had served in the administration of Bush's father and considered himself part of the extended Bush family, with the personal loyalty that kinship entailed. "It wasn't as if I was a stranger, or that anybody had to worry or could imagine that I would not be for Sonny when the time came," he later reflected. He wrote a $1,000 check to McCain and contributed an equal amount to Bush.

Worried that Powell would outshine their candidate and suspicious of his Republican credentials, Bush's handlers ignored him for most of the campaign -- even as they regularly implied to the media that the respected general was a behind-the-scenes member of the governor's brain trust. Once McCain was vanquished in the Republican primaries and Bush began a head-to-head battle against Democrat Al Gore, the campaign hinted that Powell would accompany Bush on fact-finding trips overseas and would become his secretary of state. But no one on the Bush team ever approached Powell about such a trip, and there was no substantive discussion of a Cabinet position.

Powell later recalled that the only conversations he and Bush had had about foreign affairs came just weeks before the election, in the back seats of cars between events on the four days they had campaigned together that fall. He had no memory of an explicit invitation from Bush to serve in his Cabinet. Once the U.S. Supreme Court declared the Florida recount officially over in early December, Powell later said, "It just sort of happened as it was assumed to happen."

On December 16, three days after Gore conceded defeat, Powell flew to Bush's ranch in Texas to be unveiled as his first Cabinet nominee.

Powell and Cheney stood on either side of the president-elect as he read from prepared remarks to reporters gathered in a Crawford school auditorium. Turning to Powell, Bush invoked Harry Truman's tribute to his own iconic secretary of state, retired Army general George Marshall: " ' He is a tower of strength and common sense. When you find somebody like that, you have to hang on to them.' I have found such a man." When reporters later asked Bush about tears they had seen in his eyes, he replied that it was an emotional moment because "I so admire Colin Powell -- I love his story."

THE SECRETARY OF STATE SAW THE PRESIDENT FREQUENTLY, THOUGH RARELY ALONE. Powell found Bush better-spoken and more thoughtful in private than his public posturing as a rough-hewn, plain-spoken Texan would indicate, although he found Bush's fidgety impatience irritating, along with his tendency to interrupt everyone, from his Cabinet officers to visiting heads of state. While the president publicly praised the secretary's abilities and stature, their relationship remained stiff and formal.

Powell insisted to disbelieving aides that Bush listened to, and even acted on, his advice. "The president has good instincts . . . an instinctual grasp" of issues, he often told them. But he usually followed with an acknowledgment that Bush "has got these rough edges -- his cowboy, Texan rough edges -- and when he gets them exposed, there are other people who know how to use them" to their advantage.

Time and time again during the administration's bumpy first year, Powell had seen Rumsfeld and Vice President Cheney intervene to nudge a willing Bush away from moderation and diplomacy, and toward a hard line on foreign policy issues from North Korea to the Middle East. After the September 11, 2001, terrorist attacks by al-Qaeda on New York and Washington, their attention turned sharply toward Iraq, and by the following summer it was clear that the administration was headed toward war with Saddam Hussein.

Powell found little evidence to support thinly veiled White House suggestions that Hussein had had a hand in the September 11 attacks. But he saw no reason to doubt the CIA's assessment, fervidly promoted and expanded upon by Cheney and the Defense Department, that the Iraqi leader had stockpiles of chemical, biological and perhaps even nuclear weapons, which he was ready to hand over to terrorists bent on destruction of the United States.

Powell's own war to drive Iraq out of Kuwait in 1991 had been fought with half a million U.S. troops, broad foreign support and a U.N. mandate. He believed the decision to invade was Bush's to make, but that international backing was essential for both political and military success. In August 2002, he succeeded in convincing Bush -- for once, over Cheney's objections -- that there would be no multinational support unless the administration first visibly tried to tame Hussein without war.

It took five months for Powell's efforts at the U.N. Security Council to craft a solution short of war to reach the point of collapse, caught in the crossfire of administration intransigence, international mistrust of Bush's justification and motives, and Hussein's perfidy. As the Pentagon's war plans were completed and March 2003 was secretly set as the internal deadline for invasion, Bush still found himself with little foreign support and an uncertain American public.

"We've really got to make the case" against Hussein, Bush told Powell in an Oval Office meeting in late January, "and I want you to make it." Only Powell had the "credibility to do this," Bush said. "Maybe they'll believe you." It was a direct order from his commander in chief, and it never occurred to Powell to question it.

He was told that the case had already been put together by the White House, and he assumed that with a little tweaking he could turn it into a speech that would fit his voice and style. He was taken aback on Tuesday, January 28, when he received the bulk of the document, a 48-page, single-spaced compilation of Hussein's alleged weapons of mass destruction program, replete with drama, rhetorical devices and a kitchen sink full of allegations. The most extreme version of every charge the administration had made about Hussein, the document had been written, Powell concluded, under the tutelage of Cheney's chief of staff, I. Lewis "Scooter" Libby, who shared all of his boss's hard-line views and then some.

Delivery of the speech had been set for the following Wednesday, February 5. Bush planned to announce the date that very night in his State of the Union address to Congress. Acutely aware that he would be selling his own reputation as much as the specific facts, Powell picked up the telephone to tell Condoleezza Rice, Bush's national security adviser, that he needed more time to get the speech into shape.

"Condi, please," Powell implored, "let's just tell the president that we're going to put in the State of the Union that Secretary Powell will be going to the U.N. next week. Don't put a date."

"She said, 'Right, right, of course,' " Powell recalled, "and she runs away to change the speech. Then runs back about five minutes later" to call him and say, " ' There's good news and bad news. The good news is we can change the speech.' " The bad news, she said, was that the White House had already told the media, in a preview of the State of the Union address, that Powell's presentation would be made on February 5.

"I could have gotten two more days," Powell later said wistfully. "Whether it would have made any difference or not, I don't know."

"HERE YOU GO," POWELL SAID, as he dropped the White House document on the desk of his chief of staff, Lawrence Wilkerson. Wilkerson quickly agreed it read more like a badly written novel than something designed to persuade the world. That afternoon, he assembled a State Department team-- including speechwriter Lynne Davidson and Barry Lowenkron, a senior CIA officer before he joined Powell's policy planning staff -- to set up shop at CIA headquarters, across the Potomac River in Virginia. They would examine the evidence themselves and turn the document into what Wilkerson called "a Colin Powell speech." Cheney aide John Hannah and William Tobey, the counterproliferation director at the White House National Security Council, would meet them there to answer any questions.

"We were going out to the agency and live there until we got the presentation ready," Wilkerson later said.

Their job was to make the most convincing, evidence-backed case possible. Powell had little more than a cursory knowledge of the intelligence underlying some of the most damning charges, but in recent months, as pressure built inside the administration and his frustration with the United Nations grew, Powell's language on Iraq had become almost as loose as Cheney's. In a speech to an international economic conference just the week before, he had made charges that his own State Department analysts questioned, mentioning allegations that Iraq had attempted to import uranium and nuclear-related equipment, as well as the presumed ties between Hussein and al-Qaeda.

But that had been only an indictment; this would have to be a complete, trial-worthy prosecution, designed to convince a skeptical jury that capital punishment, in the form of decapitating the Iraqi regime, was warranted.

In addition to proving the charges against Iraq, Wilkerson believed, they had to protect Powell's integrity against those within the administration who had long been out to tarnish it. There was a widespread belief among the secretary's loyal aides -- privately shared by Powell himself, although he brushed it off as meaningless political gamesmanship in conversations with them -- that both White House political adviser Karl Rove and Cheney had actively plotted to undermine him for the past three years. Powell had laughed when he described to his aides how the vice president, after a discussion of the upcoming U.N. speech, had poked him jocularly in the chest and said, "You've got high poll ratings; you can afford to lose a few points." Cheney's idea of Powell's U.N. mission, Wilkerson thought, was to "go up there and sell it, and we'll have moved forward a peg or two. Fall on your damn sword and kill yourself, and I'll be happy, too."

BY THE NEXT DAY, Wilkerson and his team were huddled in the CIA director's conference room, taking the document apart sentence by sentence. Things were not going well. Hannah had brought a clipboard with a three-inch stack of paper that he thumbed through to cite the origin of each allegation -- reports from the CIA, the Defense Intelligence Agency, foreign intelligence, the Iraqi National Congress and even newspaper articles.

CIA Director George Tenet and his deputy, John McLaughlin -- backed up by Robert Walpole, the chief CIA officer for nuclear programs; Lawrence Gershwin, the agency's top adviser on "technical" intelligence; and several other specialists -- were constantly dispatching aides to find the original source material.

In some instances, the "evidence" was, in fact, found in an official intelligence report, but only as unconfirmed information that did not appear in the report's conclusions. "They had left out all the caveats, all the qualifiers," Wilkerson recalled. In a few instances, he thought, they had even changed the meaning of the intelligence. A Senate investigation of the speechwriting process conducted after the invasion would later conclude that the Powell team had had to eliminate "information that the White House had added . . . gathered from finished and raw intelligence," some of which had come from only a single source with no corroboration at all.

By late afternoon, Tenet and Wilkerson agreed to put the White House draft aside and start over, basing the speech on a National Intelligence Estimate on Iraq that had been compiled by the CIA the previous fall.

That night, after the senior CIA and White House officials had left for the day, Wilkerson and his colleagues watched a film he had borrowed from the State Department archives of Adlai Stevenson's historic presentation to the Security Council at the height of the Cuban missile crisis in 1962.

The Soviet Union had angrily denied charges that it had deployed nuclear-armed missiles on the island 90 miles off the Florida coast. Stevenson, the U.S. ambassador to the United Nations at the time, had responded with irrefutable proof in the form of 26 grainy, poster-size black-and-white photographs of missile sites shot from a U-2 reconnaissance plane, displayed on easels at the front of the council chamber for all the world to see. That "Stevenson moment," Wilkerson told them, was the effect they were after.

Powell, Libby and Stephen Hadley, Rice's deputy, joined the process the next day.

Cheney had called Powell to say he hoped the secretary would "take a good look at Scooter's stuff." State Department spokesman Richard Boucher, who accompanied Powell to the CIA sessions, later recalled Libby himself appealing to Powell to look more carefully at the now-discarded White House material. "Powell said: 'I don't want to. I want to use what Larry's been working on.' "

They settled into a routine over the next few days. The CIA turned over the office suite of the National Intelligence Council -- the internal organization that coordinated with other members of the intelligence community to write National Intelligence Estimates -- to Wilkerson and the others engaged in the nitty-gritty of composing the speech and providing material to the graphic designers lodged in the agency's basement. At around 5 p.m., the writing and research team would move to Tenet's conference room with senior officials, eventually including Rice and Armitage, to spend hours going over the new text and verifying the sourcing for Powell.

Powell insisted that they eliminate any intelligence that had come from Ahmed Chalabi, an Iraqi exile favored by the Pentagon and the vice president's office, but widely mistrusted as a charlatan within the State Department. Powell was told by the CIA that evidence that Hussein had built mobile laboratories to conceal his biological weapons programs -- one of the most damning charges -- had been corroborated by four separate sources, including an Iraqi chemical engineer, a civil engineer and an Iraqi military defector. It was, Tenet said, "totally reliable information."

They argued over how to interpret intercepted communications about Iraq's weapons between Iraqi military officers. None seemed definitive, and Wilkerson was worried that they might not mean what the analysts said they meant. But amid the scant information the CIA officials were willing to declassify for public consumption, they said this was the best they had.

The team examined satellite imagery said to reveal prohibited items. Powell was shown, and rejected, a grainy picture of what analysts said was an unmanned aerial vehicle (UAV) site near Basra. It was impossible to tell where it was or even what it was, he argued. Instead, he approved a U.N. photograph of a generic Iraqi UAV, taken years earlier, to illustrate charges that Hussein was developing drones that could spray deadly weapons of mass destruction on population centers.

CIA analysts showed the team additional photographs they said conclusively revealed chemical weapons production and storage facilities, but then insisted that the pictures were too sensitive to be used in a public presentation. Those they were willing to release often appeared -- at least to the uninitiated in the room -- to illustrate nothing more than trucks parked beside buildings. "Don't you have a picture of chemical weapons canisters being moved around?" Boucher later recalled asking Tenet. "Something we can point to and say: 'That's a chemical weapon.' " Tenet replied that no country had left prohibited weapons "out on the lawn" since the Cuban missile crisis. "They know we're looking at them. So we have to go with other things that tell us what they're doing."

They spent hours discussing the aluminum tubes Hussein had tried to import. The Energy and State departments continued to disagree with the CIA's assessment that the tubes were designed for nuclear enrichment. McLaughlin, who had brought one of the intercepted tubes to the table and rolled it back and forth as they argued, insisted that the CIA analysis was correct. The agency, Powell later recalled, "pulled in their experts and swore on a stack of Bibles that they'd done every analysis imaginable, and [the tubes] simply were not for rockets, but for [uranium] centrifuges." The tubes stayed in the speech, although with a brief mention of the disagreement among U.S. government agencies as to their purpose. (U.S. investigators in Iraq after the war later concluded they were meant for rockets.)

Bush had referred in his State of the Union address to Iraqi efforts to obtain uranium from Africa -- the same information the CIA had successfully argued should be excised from a speech he gave the previous October because of questionable sources. No one suggested that it be included in Powell's presentation.

The White House document detailing Hussein's ties to terrorism was, if anything, even more problematic than the portion on weapons of mass destruction.

Powell retreated with Tenet to the director's private office to talk through "what we really know" about the relationship between Iraq and al-Qaeda. Powell was shown the transcript of an interrogation of a captured Osama bin Laden aide who swore that al-Qaeda operatives had received biological and chemical weapons training from Iraq, and the charge became a lengthy portion of the speech. (A year after the invasion, the agency acknowledged that the information had come from a single source who had been branded a liar by U.S. intelligence officials long before Powell's presentation.)

Tempers began to fray as the sessions continued into the weekend. Tenet and McLaughlin became irritated with Hadley, who kept pressing to reinsert jettisoned White House language and information. Powell exploded at McLaughlin, who supplied tortured, five-minute answers to seemingly simple questions. Increasingly, the secretary looked to Tenet for reassurance. "George would give the kind of answers the secretary liked," Wilkerson recalled. "Whether you liked that 'slam-dunk' language or not, George, to his credit, would say, 'Absolutely, Mr. Secretary, I stand by that.' "

Powell later recalled that most of their time was spent "trimming the garbage" of the White House's overwrought verbiage and uncorroborated specifics from the speech. Once that was done, Wilkerson concluded long afterward, "what we were all involved in -- groupthink isn't the right word -- it was a process of putting the data to points in the speech rather than challenging the data itself." As they probed for proof of Hussein's lies, no one thought of looking for evidence that might have raised questions about their assumptions that the weapons existed.

WHEN HE ARRIVED IN NEW YORK ON MONDAY AFTERNOON, Powell was as nervous as Wilkerson had ever seen him. He was worried that the language in the speech was still too methodical and technical to win over an audience. Powell's best performances were modeled on what he had learned as a young instructor at Fort Benning and later at the Pentagon: Use a map or some slides, a rough outline or a few key phrases, and then speak naturally. He always knew his material cold, but it was technique that clinched a sale. This time, however, each sentence had been carefully crafted and debated ad nauseam, and he was going to have to read directly from the text.

On Tuesday night, the team had a final, full-dress rehearsal. The cafeteria on the top floor of the U.S. Mission to the United Nations had been reconfigured into a mock-up of the Security Council chamber. Powell used a stopwatch to check his timing, clicking it off every time someone interrupted with a question or comment. The speech was 75 minutes long.

When he finished, the tension of the last several days seemed to dissipate like the air escaping a balloon, leaving him calm and tired. He believed he had done everything he could do. Departing for his room at the Waldorf, where he hoped to get a good night's sleep, he reminded Tenet that "you're going to be there with me tomorrow." He expected the CIA director to sit in full view of the television cameras, just behind him at the Security Council table. Tenet replied, only half-jokingly, that he was the one who would have to face the intelligence committees in Congress if there were any mistakes. Powell told his executive assistant, Craig Kelly, and Boucher to make sure that Tenet was waiting in the side room they would pass through on their way into the Security Council chamber the next morning. Later, he changed his mind and called Tenet to tell him he would swing by the CIA director's hotel and pick him up on the way to the United Nations, just to make sure there were no glitches.

On Wednesday, February 5, Powell entered the chamber just before 10:30 a.m., smiling and stopping to shake hands as he made his way across the floor. With war hanging in the balance, and the power and prestige of the United States on full display, it was a moment of high drama that owed as much to the player as to the play. A nationwide poll released just that morning had found that "when it comes to U.S. policy toward Iraq," Americans trusted Powell more than Bush by 63 to 24 percent.

"I cannot tell you everything that we know," he began after a brief introduction. "But what I can share with you, when combined with what all of us have learned over the years, is deeply troubling." The facts and Iraq's behavior "demonstrate that Saddam Hussein and his regime have made no effort -- no effort -- to disarm as required by the international community."

"My colleagues," Powell said, "every statement I make today is backed up by sources, solid sources. These are not assertions. What we are giving you are facts and conclusions based on solid intelligence."

The next day, opinion polls indicated that national opinion had shifted literally overnight; most Americans surveyed said they believed an invasion was justified to protect the nation. Those closest to Powell were relieved, but worried about both him and the nation. His wife, Alma, had a sense of foreboding; her husband, she thought, was being used by the White House. Powell's daughter Linda, who had listened to the speech on the radio, had found his performance unsettling. His voice was strained, she thought, as if he were trying to inject passion into the dry words through the sheer force of his will.

Wilkerson, who had left the United Nations immediately after the speech and returned to his hotel room to fall into a deep sleep, awoke depressed. Later, when it became clear that much of the speech on which he had worked so hard was based on lies, he would come to think of that week as "the lowest moment of my life." Back in Washington, he ordered special plaques with Powell's signature made up for the State Department aides who had worked so hard to make the presentation happen.

When they were handed out, Powell asked Wilkerson why he hadn't ordered one for himself. Wilkerson replied that he didn't want one.

AS 2004 BEGAN, U.S. TROOPS WERE HEADED TOWARD A SECOND YEAR IN THE IRAQI QUAGMIRE. No weapons of mass destruction had yet been found, and each day's news brought fresh indications that the administration had exaggerated its case against Hussein. Powell's own prominent role came under increasing question. It was now clear that "a lot of probables, a lot of maybes" had been left out of the assessment of Iraq's capabilities, a reporter confronted him. Given a second chance, would he have "rephrased" his U.N. speech?

"No," Powell replied firmly. "I knew exactly the circumstances under which I was presenting that speech . . . The whole world would be watching, and there would be those who would applaud every word, and there would be those who were going to be skeptical of every word." Whatever doubts were now being raised, he said, the basic conclusions had been solid. "I am confident of what I presented last year. The intelligence community is confident of the material they gave me; I was representing them . . . they stand behind it."

But on Friday, January 23, the CIA announced without explanation that David Kay, the head of its Iraq Survey Group hunting for weapons of mass destruction, was being replaced. Later that day, Kay told reporters he doubted the weapons existed. When Congress demanded answers, Kay said the same thing.

As Powell flew the next day to attend a presidential inauguration in the Republic of Georgia, journalists aboard his plane asked him to reconcile his U.N. speech with Kay's conclusions. "You said a year ago that you thought there was between 100 and 500 tons of chemical weapons [in Iraq]," one reporter said. "Who's right?"

"I think the answer to the question is I don't know yet," Powell replied.

"What is the open question is: how many stocks they had, if any? And if they had any, where did they go? And if they didn't have any, then why wasn't that known beforehand?"

Powell thought there was no sense denying the obvious questions Kay had raised. But it was the first doubt that any senior administration official had publicly expressed about the central justification for the war. The story made headlines around the world, and an agitated Condoleezza Rice called him the next morning in Georgia. Powell was not surprised; it was not the first time that the White House had blown up at him over what he considered honest comment. Rice, he later recalled, was usually the one to make the call. "She'd say, 'Oh, we've got a problem, what are we going to do about this? How are we going to fix this?' "

On this issue, he thought, there was little to be done. "The fact of the matter is, you can't ignore the possibility, since the guy we sent there for eight months as our guy says there's nothing there," he later recalled telling Rice with exasperation. "So, to say there's got to be something there when he, who has been there for eight months, says there's nothing there . . . You can't do that. You've got to at least accept the possibility."

The White House, he advised, should "just be quiet" for now.

ON HIS RETURN, POWELL SPENT THE WEEKEND carefully reading Kay's congressional testimony, highlighting portions with a yellow marker and scribbling notes in the margins. With the first anniversary of his U.N. speech just days away, the Sunday newspapers and television talk shows were filled with comparisons between the charges he had made and Kay's conclusions.

On Monday, February 2, he arrived for an interview at The Washington Post carrying a blue folder with the marked-up testimony inside. He was "absolutely convinced" that the invasion had been the right thing to do, Powell emphatically told the two dozen reporters and editors crowded around a conference table in the newspaper's eighth-floor boardroom.

Would he still have "recommended the invasion" if Tenet had told him a year before "that there are no stockpiles?" one reporter asked.

"I don't know, because it was the stockpiles that presented the final little piece that made it more of a real and present danger and threat to the region and to the world," Powell replied. But there was no point discussing hypotheticals, he said, because "the fact of the matter" was that the CIA, as well as intelligence agencies in Britain and elsewhere, had "suggested the stockpiles were there."

But what if he had known they weren't there? the reporter pressed.

"The absence of a stockpile changes the political calculus," Powell acknowledged. "It changes the answer you get with the little formula I laid out."

To a White House already reeling from the one-two punch of Kay's conclusions and Powell's comments en route to Georgia, it was another worrisome example of the secretary of state's unwillingness to stay "on message." When his remarks appeared in The Post the next morning, "I think the whole White House operation was mad . . . the NSC, the president -- everybody was annoyed," Powell recalled. "White Houses do not respond well to immediate problems in the morning . . . all the white corpuscles race to the source of the infection, so all the white corpuscles raced to me."

After Rice's inevitable irate telephone call, presidential aides quickly began contacting the media to counteract the secretary's remarks. Annoyed but not surprised, Powell issued a White House-requested "clarification" insisting that Hussein had had the "capability and intent" to produce the weapons even if none had yet been found. Bush, he repeated, had been right to invade.

Still mulling over the situation a week later with a visitor in his dimly lit office, he criticized a persistent White House machismo that took aim at "anything . . . that suggests any weakness in the [administration's] position," regardless of common sense. That, and what he saw as a never-ending effort to humble him personally.

"There are people who would like to take me down," he said, jerking his thumb in the direction of the White House. "It's been the case since I was appointed. By take down, I mean 'keep him in his place'. . . And there are those who, whether it was me or anyone else, just love somebody getting in trouble, because it's usually to the detriment of the person getting in trouble and to the advantage of someone else."

The episode reinforced his already deep-seated disdain for politics and its practitioners. Political thought and decision-making were often polluted by ideology and the exigencies of the election cycle; soldiers breathed a purer, more rational air. "I was not trained as a politician or a think tank guy or anything else," Powell insisted. "I was trained to consider all possibilities."

"I mean, if you're attacking and suddenly you get attacked from the flank," he continued, using his hands to illustrate a military maneuver, "you don't say, 'I'm going to keep attacking straight ahead [and] ignore this new threat coming at my flank.' " He had been asked whether different information would have changed his assessment of the Iraq situation, and "all of my instincts and all of my background and training at that point said the answer to the question is, 'I'd have to reconsider.' "

He shrugged and brought his hands to rest. "But that's the way it goes."

Powell's irritation at the White House was coupled with a growing anger at the CIA. Right or wrong, at least Bush had willingly shouldered the ultimate responsibility for the decision to go to war. Powell felt he had done his own duty by privately voicing caution even as he gave the president his full support. But it was increasingly apparent that the intelligence community had been careless with the truth and hence with Powell's most precious commodity -- his credibility with the American people.

For a week after Kay's report, the CIA had continued publicly to stand by its prewar weapons assessment. But in a hastily arranged speech at Georgetown University on February 5, Tenet finally admitted the possibility of error. His "provisional bottom line," he said, was that the intelligence community had been "generally on target" in its warnings that Hussein was developing long-range missiles. But the CIA "may have overestimated the progress Hussein was making" on nuclear weapons.

As for biological weapons stockpiles and mobile laboratories, he said, "we are finding discrepancies in some claims made by human sources" to whom the agency "lacked direct access." The CIA, Tenet said, "did not ourselves penetrate the inner sanctum" of Hussein's programs but had "access to emigres and defectors" along with high-level information from "a trusted foreign partner." They were now in the process of "evaluating" questions such as, "Did we clearly tell policymakers what we knew, what we didn't know, what was not clear, and identify the gaps in our knowledge?"

Although Powell had been advised in recent months of problems with some of the intelligence sourcing, Tenet's speech was "the first time I heard that the CIA was no longer sticking behind its story" in public, he later recalled. He had been given no advance copy of the CIA director's remarks and listened in his office to a broadcast of Tenet's acknowledgment of "discrepancies" and uncertainties.

Powell stared silently at Wilkerson after Tenet finished speaking. "But the question is," Wilkerson said, reaching for a joke, "are you still friends?"

"I don't think so," Powell replied.

As the evidence continued to unravel, some in the media suggested that Powell should apologize publicly for peddling false information that had pushed the nation toward war. "Is everyone else going to apologize?" he railed within the four walls of his office. "It's not [just] me getting had. I'm not the only one who was using that intelligence . . . they all stood up in the Senate. The president stood up on this material. [British Prime Minister] Tony Blair stood up on this material . . . The whole global intelligence community bears responsibility."

But there was no denying that he had been the most visible and effective salesman. He already knew that the label would follow him around forever. "I'm the guy who will always be known as the 'Powell Briefing' . . . I'm not being defensive, because I did it. But Powell wasn't the only one."

PRESENTATION WAS NEARLY AS IMPORTANT TO POWELL AS SUBSTANCE, and after his inelegant dismissal as secretary of state, he wanted at least to control the way his departure was announced. After submitting his letter on Friday, he spent the weekend putting together a plan: He would inform his inner-office staff at exactly 8:20 a.m. the following Monday, November 15. He would tell his senior aides at their regular 8:30 staff meeting. At 10:15, he would send an e-mail to his friends and extended family. He called Card and told him he expected the White House would then publicly announce his resignation.

At midmorning Monday, the White House released five separate statements under Bush's name, reporting the resignations of the secretaries of agriculture, energy, education and state, and the head of the Republican National Committee. Each statement was three paragraphs long and titled "President Thanks [official's name]." When White House spokesman Scott McClellan briefed the media shortly after noon, all but one of the resignation questions were about Powell. Had Bush tried to persuade him to stay? Had Powell offered? If so, had the president turned him down? McClellan avoided a direct answer. "I think you saw from Secretary Powell's letter that this is a discussion that they've had for some months now, or over recent months at least . . . And Secretary Powell made a decision for his own reasons that this was now the time to leave."

The next morning, Bush nominated Rice as his new secretary of state.

Powell saw Bush regularly over the next two months, passing through the Oval Office for routine meetings that took place as if nothing had transpired. Eventually, the White House contacted his office to schedule what it described as a "farewell call" with the president. Such calls were being arranged for each departing Cabinet secretary.

When Powell saw the January 13 appointment on his calendar, his staff told him they assumed it was a goodbye photo opportunity with Bush. They suggested that perhaps he should bring his family.

"We've got a houseful of pictures," Powell replied dryly. Was he supposed to talk to the president? Or was the president supposed to talk to him?

"Am I supposed to say: 'This is what I think?' Or what?"

He didn't have to say anything, he was told. It was just a "farewell call."

As the meeting approached, the White House -- which had scheduled it in the first place -- inexplicably called the State Department to ask for "talking points" that aides could use to brief the president.

The appointed time found Powell already in the Oval Office for a routine meeting; when it concluded, he lingered as the others left. As Powell later remembered it, Bush seemed puzzled and called after his departing chief of staff, "Where you going, Andy?"

"Mr. President, I think this is supposed to be our farewell call," Powell prompted.

"Is that why Condi ain't here?" he recalled the president asking.

That was probably the reason, Powell replied.

Card walked back inside, and the three men sat down. Powell had already decided to use the opportunity -- likely his last as secretary of state -- to unload.

The war in Iraq was going south, he said after a few moments of small talk, and the president had little time left to turn it around. The administration's hope was that the upcoming election there would change the dynamics on the ground, and the Iraqi people would finally be ready and able to begin standing up to the insurgents on their own.

But the administration, he pointed out, had entertained such hopes before over the past two years -- when it had set up a new legal framework for Iraq, when it had first turned a modicum of government power over to handpicked Iraqis and when ousted dictator Saddam Hussein had been captured -- and those hopes had been dashed every time. There would be a window of about two months after the election "to start to see progress," he told Bush. "If by the first of April this insurgency is not starting to ameliorate in some way, then I think you really have a problem."

Elections, and talking about democracy, were unlikely to stop the insurgency, he said. Only the fledgling Iraqi army could do that, and it was unclear whether it would ever succeed. Its competence was not just a matter of training, Powell said; it was a question of whether the troops believed in what they were fighting for.

Powell warned about serious internal problems in Bush's own administration, saying that the power he had given the Pentagon to meddle in diplomacy on issues as widespread as North Korea, Iraq and the Arab-Israeli conflict, along with poisoned personal relations between his State and Defense departments, were seriously undermining the president's diplomacy. Bush dismissed his concern. It wasn't any worse, he said, than the legendary battles between State and Defense during the Reagan administration.

The session ended with a cordial handshake, and the secretary returned to the State Department. "That was really strange," he reported to Wilkerson. "The president didn't know why I was there."

Karen DeYoung is an associate editor of The Post. This article is excerpted from Soldier: The Life of Colin Powell, being published October 10 by Knopf. She will be fielding questions and comments about this article Monday at noon at washingtonpost.com/liveonline.