WASHINGTON — Robert S. McNamara, the cerebral secretary of defense who was vilified for carrying out the Vietnam War, then devoted himself to helping the world's poorest nations, died Monday. He was 93.

McNamara died at 5:30 a.m. at his home, his wife Diana told The Associated Press. She said he had been in failing health for some time.

For all his healing efforts, McNamara was fundamentally associated with the Vietnam War, "McNamara's war," the country's most disastrous foreign venture, the only American war to end in abject withdrawal rather than victory.

Known as a policymaker with a fixation for statistical analysis, McNamara was recruited to run the Pentagon by President John F. Kennedy in 1961 from the presidency of the Ford Motor Co. He stayed seven years, longer than anyone since the job's creation in 1947.

His association with Vietnam became intensely personal. Even his son, as a Stanford University student, protested against the war while his father was running it. At Harvard, McNamara once had to flee a student mob through underground utility tunnels. Critics mocked McNamara mercilessly; they made much of the fact that his middle name was "Strange."

After leaving the Pentagon on the verge of a nervous breakdown, McNamara became president of the World Bank and devoted evangelical energies to the belief that improving life in rural communities in developing countries was a more promising path to peace than the buildup of arms and armies.

A private person, McNamara for many years declined to write his memoirs, to lay out his view of the war and his side in his quarrels with his generals. In the early 1990s he began to open up. He told Time magazine in 1991 that he did not think the bombing of North Vietnam — the biggest bombing campaign in history up to that time — would work but he went along with it "because we had to try to prove it would not work, number one, and (because) other people thought it would work."

Finally, in 1993, after the Cold War ended, he undertook to write his memoirs because some of the lessons of Vietnam were applicable to the post-Cold War period "odd as though it may seem."

"In Retrospect: The Tragedy and Lessons of Vietnam" appeared in 1995. McNamara disclosed that by 1967 he had deep misgivings about Vietnam — by then he had lost faith in America's capacity to prevail over a guerrilla insurgency that had driven the French from the same jungled countryside.