McNamara was the Secretary of Defense under Presidents Kennedy and Johnson. He served for 7 years -- the longest tenure of any Defense Secretary. McNamara was known for his cerebral ways and for his fixation with statistical analysis.
As a professor at the Harvard Business School when World War II started, he helped train Army Air Corps officers in cost-effective statistical control. In 1943, he was commissioned an Army officer and joined a team of young officers who developed a new field of statistical control of supplies.
After the war, McNamara and his colleagues joined Ford Motors and revitalized the company. The group became known as the "whiz kids" and McNamara was named the first Ford president who was not a descendant of Henry Ford.
But just a month after becoming Ford's president, the newly elected Kennedy asked McNamara to be his Defense Secretary. Taking the $25,000-a-year job cost McNamara millions of dollars in salary and stock options he would have received from Ford.
McNamara was an ardent supporter in the early days of the Vietnam War. But as the years went on and casualties rose, in 1967 McNamara recommended to President Johnson a bombing halt and a freeze on troop levels. Johnson lost faith in McNamara, and he was done. McNamara later said he didn't know whether he quit or was fired.
McNamara would go on to head the World Bank for 12 years before retiring in 1981. Since then, he has become a global elder statesman, working behind the scenes on such issues as nuclear disarmament.
After long resisting to writing his memoirs, he finally published "In Retrospect: The Tragedy and Lessons of Vietnam" in 1995. In it, he admitted the war was ultimately a mistake. He said in an interview at the time:
"We of the Kennedy and Johnson administrations acted according to what we thought were the principles and traditions of our country. But we were wrong. We were terribly wrong."
McNamara re-entered the public conversation when the second Iraq War started in 2003. With its similarities to Vietnam, McNamara's opinion was highly sought. Over the years, he met twice with then President Bush to discuss war policies.
Also that year, the documentary "The Fog of War: Eleven Lessons from the Life of Robert S. McNamara" was released. With war raging in Iraq, it was extremely popular and won the Oscar for best documentary feature.
McNamara's first wife, Margaret, whom he met in college, died of cancer in 1981. They had two daughters and a son. In 2004, at age 88, he married Diana Masieri Byfield.