WASHINGTON

Robert S. McNamara, the former secretary of defense whose record as a leading executive of industry and a chieftain of foreign financial aid was all but erased from public memory by his reputation as the primary architect of U.S. involvement in the war in Vietnam, died yesterday at age 93.

Diana McNamara said her husband died at his home in Washington. She did not give a cause of death.

Mr. McNamara was secretary of defense during the presidencies of John F. Kennedy and Lyndon B. Johnson. In that capacity he directed a U.S. military buildup in Southeast Asia during the critical early years of a Vietnamese conflict that escalated into one of the most divisive and bitter wars in U.S. history. When the war was over, 58,000 Americans were dead and the national social fabric had been torn asunder.

Before taking office as secretary of defense in 1961, Mr. McNamara was president of Ford Motor Co. For 13 years after he left the Pentagon in 1968, he was president of the World Bank. He was a brilliant student, a compulsive worker and a skillful planner and organizer, whose manifest talents carried him from modest circumstances in California to the highest levels of the Washington power structure.

After his retirement from the bank in 1981, he maintained an exhausting schedule as director or consultant to scores of public and private organizations and was a virtual one-man think tank on nuclear arms issues.

But more than 40 years after the fact, he was remembered almost exclusively for his orchestration of U.S. prosecution of the war in Vietnam, a failed effort by the world's greatest superpower to prevent a Communist takeover of a weak and corrupt ally. For his role in the war, Mr. McNamara was vilified by harsh and unforgiving critics, and his entire record was unalterably clouded. For the rest of his life, he would be haunted by the Vietnam ghosts.

In his 1995 memoir of the war, "In Retrospect: The Tragedy and Lessons of Vietnam," Mr. McNamara said he and his senior colleagues were "wrong, terribly wrong" to pursue the war as they did. He acknowledged that he failed to force the military to produce a rigorous justification for its strategy and tactics, misunderstood Asia in general and Vietnam in particular, and kept the war going long after he realized it was futile because he lacked the courage or the ability to turn Mr. Johnson around.

He elaborated on Vietnam and the other events that shaped his life in Errol Morris' Academy Award-winning documentary "The Fog of War: Eleven Lessons from the Life of Robert S. McNamara" (2003). He described how as a young man he had analyzed bombing operations under the command of Gen. Curtis LeMay during World War II and in that job played a role in making the firebombing of dozens of Japanese cities "more efficient."

"We burned to death 100,000 Japanese civilians in Tokyo -- men, women and children," he told Mr. Morris. "LeMay recognized that what he was doing would be thought immoral if his side has lost," he added. "But what makes it immoral if you lose and not immoral if you win?"

From the day in 1961 when he burst upon the Washington scene as a political unknown selected by Mr. Kennedy to be secretary of defense, Mr. McNamara's trim figure, slicked-back hair and rimless glasses made him instantly recognizable, a Washington monument whose interests covered everything from nuclear war to the fiscal health of local governments.

At the Pentagon, he reorganized the military bureaucracy, built up the country's nuclear arsenal and instigated a massive campaign to end racial discrimination in off-base housing. At the World Bank, he was often described as "the conscience of the West," for his relentless efforts to persuade the industrialized world to commit more capital to improving life in the have-not nations.

As secretary of defense, he was a key figure in such major crises as the Bay of Pigs fiasco and the Cuban missile confrontation with the Soviet Union. He changed the balance of nuclear forces in the world with the development of the multiple-warhead missile.

His reputation foundered in Vietnam. Many Americans held him largely responsible for the futile and humiliating military adventure there, a responsibility he accepted in a 1995 memoir of the war.

It was "McNamara's war," matching his technology, statistics, weaponry and organization charts against a peasant army from a small, impoverished country. The peasants won. In retrospect, it could be seen that Mr. McNamara's can-do, technological approach to military issues might have been perfectly suited to a conflict against the Soviet Union in Europe, but it led him into disastrous miscalculations in the jungles and paddies of Vietnam.

On his first visit to South Vietnam in 1962, before most Americans had heard of the place and before the involvement of American combat forces, Mr. McNamara said that "every quantitative measurement we have shows we're winning this war."

It was a statement often quoted by his critics in later years, because it seemed to encapsulate the fallacy of his approach. American troops did prevail in many of the big battles, and the United States did win the war by every statistical measurement on the Pentagon charts that Mr. McNamara so admired. But the numbers -- even the few that were accurate -- had little to do with the political reality on the ground.

In fact, despite his addiction to charts, statistics and briefings in which the United States and its ally in Saigon were always winning, Mr. McNamara privately had a broader appreciation of what was happening in Vietnam. As early as 1964, after Buddhist uprisings that shook Saigon's political structure, he observed that the Viet Cong had "large indigenous support" and were held together by "bonds of loyalty." In 1966, even as the buildup of U.S. forces continued and Cold War tensions gripped Europe, he said it was "a gross oversimplification to regard Communism as the central factor in every conflict throughout the underdeveloped word . . `. The United States has no mandate from on high to police the world and no inclination to do so."

Mr. McNamara acknowledged late in his Pentagon tenure that the bombing of North Vietnam and the Ho Chi Minh trail supply line could not cripple the Viet Cong because the Viet Cong hardly needed any supplies other than ammunition. But as critics pointed out and as he admitted many years later, he was unable or unwilling to translate these assessments into policy reversals that would extricate the Johnson administration from the Asian morass.

The harshest critic of all, journalist and author David Halberstam, describing Mr. McNamara's trips to Saigon, wrote in "The Best and the Brightest" that Mr. McNamara, the ultimate technocrat, was "a prisoner of his own background ... unable, as indeed was the country which sponsored him, to adapt his values and his terms to Vietnamese realities. Since any real indices and truly factual estimates of the war would immediately have shown its bankruptcy, the McNamara trips became part of a vast unwitting and elaborate charade, the institutionalizing and legitimizing of a hopeless lie."

In Mr. Halberstam's judgment, Mr. McNamara "did not serve himself or his country well. He was, there is no kinder or gentler word for it, a fool."

Chester L. Cooper, a senior official at the State Department when Mr. McNamara was at Defense, wrote in "The Lost Crusade" that Mr. McNamara's brilliant staff and his "unique ability to grasp and synthesize a vast mass and variety of information made him the best informed official in Washington." But Mr. McNamara's insistence on dealing with Vietnam in the same way he dealt with other issues led him into miscalculations, Mr. Cooper said. For all his participation in the great events of his time, it was the Vietnam war that shaped the nation's perception of Mr. McNamara and his performance, and eventually eroded his credibility. When he said, in 1966, that manpower requirements and draft calls would be reduced in the following year, hardly anyone seemed to believe him. When he told Congress that the purpose of bombing the Ho Chi Minh trail was to reduce North Vietnamese troop infiltration into the South, newspaper analysts pointed out that the Pentagon's own charts showed infiltration was increasing.

An incident that reflected the temper of those tense, bitter years occurred in November 1966, when Mr. McNamara traveled to Harvard for an informal discussion with undergraduates. He was mobbed by about 800 jeering students, who blocked his car and cried "murderer."

The secretary, never apologetic, climbed atop his car, in shirt sleeves despite the New England chill, and told the crowd, "I spent four of the happiest years of my life on the Berkeley campus, doing some of the things you do today. But I was tougher than you, and I'm tougher than you are now. I was more courteous then, and I hope I'm more courteous today."

It is inaccurate to portray Mr. McNamara as an unreconstructed hawk to the bitter end; his early doubts became known after the war. But he failed to persuade the president and such hard-line White House insiders as national security specialist Walt W. Rostow to moderate their views. Mr. McNamara succeeded only in hastening his own ouster from the Cabinet, and because he waited 20 years after the fall of Saigon in 1975 to go public with his confession of error about the war, he retained his reputation as a technocrat committed to firepower above all else.

Mr. McNamara later dismissed as "absurd" and "baloney" suggestions that he devoted himself to helping Third World countries through the World Bank to atone for his record in Vietnam. But he never attempted to defend himself against critics of his role in Vietnam, or to justify the escalation there. For more than two decades after leaving the Pentagon he avoided the topic of Vietnam in his public statements.

Even when testifying under oath, as he did in the 1984 trial of a libel suit against CBS filed by the former U.S. troop commander in Vietnam, Gen. William C. Westmoreland, Mr. McNamara remained resolutely nonjudgmental about the conduct of the war. He testified that unlike Gen. Westmoreland and senior White House officials at the time, he began to believe as early as 1965 or 1966 that the war "could not be won militarily." But he added, "I say this without saying that I was right and they were wrong."

Publication of his 1995 memoir opened some kind of intellectual floodgate for McNamara; he developed a virtual fourth career of organizing and participating in seminars about the war -- about who did what and why, and about how doing something else might have meant, if not a different outcome, at least less death. In 1999 he published a book about this quest for the truth about the war, with a title signaling that he did not find it: "Argument Without End: In Search of Answers to the Vietnam Tragedy."

Thus in the final years of his life, the war again took over the reputation of a man whose life in many ways had embodied the American dream.

Robert Strange McNamara was born June 9, 1916, in San Francisco, where his father was sales manager for a wholesale shoe company. He demonstrated academic brilliance from the time he was in elementary school, and achieved straight A's in high school. At the University of California in Berkeley, where he studied economics and philosophy, he was elected to Phi Beta Kappa after his sophomore year.

After graduation in 1937, he went to the Harvard Graduate School of Business Administration, where he earned his MBA degree in 1939. He went back to the West Coast for a year, to work for the accounting firm of Price, Waterhouse & Co., and during that time he married a former classmate, Margaret Craig. She died in 1981.

In 1940, Mr. McNamara returned to Harvard as an assistant professor. When the United States entered World War II, he volunteered for military service but was initially rejected because of weak eyesight. He worked closely with the military, however, teaching courses for officers and serving as a consultant to the Army Air Corps on the establishment of a statistical system for the control of logistical operations.

He took a leave from Harvard to go to England on a military mission in 1943, and there he was finally granted a commission and accepted into the service as a captain.

In three years of active duty, he traveled in several Asian countries. He later said that it was the experience of visiting Calcutta during a famine, when there were as many dead people in the streets as live ones, that first stirred his interest in trying to improve conditions in the poorest nations.

The Kennedy administration came into office vowing to close the "missile gap," the apparent Soviet lead in strategic nuclear weapons. Mr. McNamara later acknowledged that there was no "missile gap" -- he said it was based on "a total misreading of the information" -- but by that time the United States had greatly expanded its nuclear arsenal and the Soviets had responded in kind.

Mr. McNamara sponsored development of missiles that could carry up to 14 nuclear warheads each, giving the United States the ability to strike more and more Soviet targets without adding any more missiles and the capability of launching more warheads than the Soviets could fend off. This, Mr. McNamara later acknowledged, was substantially responsible for the nuclear arms race.

"I have no question," he said in a 1982 interview, "but that the Soviets thought we were trying to achieve a first-strike capability. We were not. We did not have it. We could not attain it; we didn't have any thought of attaining it. But they probably thought we did." Their response, he said, provoked a counter-response by the United States, and the cycle became self-perpetuating.

He was at the center of Washington decision-making during the 1962 confrontation with Moscow over the installation of Soviet nuclear missiles in Fidel Castro's Cuba.

Mr. McNamara never publicly broke with Mr. Johnson over the war in Vietnam, but a gradual process of disillusionment seemed to set in as he lost control of tactics to the generals.

Even when he resigned to move to the World Bank, Mr. McNamara remained publicly loyal, staying on as secretary for a transition period of several months until his successor, Clark Clifford, took over in early 1968.

Unlike other high government officials who seemed to spend their years out of power waiting around Washington for a chance to get back in, once he moved from the Pentagon to the World Bank Mr. McNamara threw himself into his new assignment with zest, and concentrated on using the bank's resources to help alleviate the poverty of the most backward nations.