“We were wrong, terribly wrong”, declared Robert McNamara two decades after the end of the Vietnam War in a dramatic confession of culpability for a disastrous conflict that he came to believe America should never have fought. No American official bore greater responsibility for the war he managed and pursued with such determination for seven years as US Defence Secretary.

When he took over in the new Kennedy administration in 1961, America had just a handful of military advisers and special forces in Vietnam. When he resigned from the Johnson administration in 1968 there were half a million US forces in Vietnam fighting in America’s most divisive war since the Civil War.

Back in 1961 McNamara was the leading member of Kennedy’s “Whiz-kids” — bright, energetic young men who combined intellectual qualities with strong practical streaks. He brought modern business management techniques to the Army, Navy and Air Force and an alarming certainty that he was right.

He was one of the most powerful and influential men in the Kennedy cabinet, some said he was second only to Kennedy himself. By 1965 he seemed to dominate the nation’s affairs to the extent that the only voice clearly above his was that of President Lyndon Johnson. He won the huge admiration of Johnson who once said: “he represents the best of America”. He ran the Pentagon in a fashion similar to the way he ran the Vietnam War, exercising the same degree of personal control and supervision.

In 1963, at the time of the Kennedy assassination, only 78 Americans had been killed in Vietnam. In 1965 McNamara advised Johnson to go for an all out military victory and from then on it became known in some circles as McNamara’s War. The final result was an American death toll of 56,000.

In 1968, with mounting casualties and violent domestic unrest, McNamara decided at last that the war was unwinnable. He abandoned Johnson and resigned to become President of the World Bank. He maintained a self-imposed silence about the Vietnam war throughout his twelve years at the World Bank and afterwards, until in 1995 he published a book entitled In Retrospect: the Tragedy and Lessons of Vietnam. In an extraordinary admission he blamed himself and other top officials of the Kennedy and Johnson administrations for countless errors and ill-founded judgments.

During a television interview to promote the book he broke down in tears. “We could and should have withdrawn from Vietnam” in 1963 around the time of the Kennedy assassination, he wrote, adding that he thought Kennedy “probably would have pulled us out” had he survived. He said he no longer believed in the “domino theory” he had once proclaimed; that he had underestimated the power of nationalism in the region; that he had failed to appreciate the limits of American high-tech military equipment; and that he regretted not drawing Congress and the American people into a frank debate about the war. He also admitted that “we, as a Government, failed to address the fundamental issues” and overlooked the military, political, financial, and ultimately the human costs of the war.

Robert Strange McNamara was born in San Francisco in 1916, the son of the manager of a shoe manufacturing firm. Disciplined, abstemious and a Presbyterian, he displayed, said one interviewer, a disturbing immunity to self-doubt with a strong streak of idealism. Apart from a period when he ran away to sea, his education followed the familiar pattern of the American meritocracy: he studied for a degree at the University of California and was a member of the Phi Beta Kappa fraternity. He went on to take an MA at the Harvard Business School and undertook war service in the US Air Force.

With nine of his contemporaries — the original “Whiz-kids” — he negotiated a joint contract with the Ford Motor Company, and deployed the latest in cost benefit analyses and other modern statistical techniques. In November 1960 he became president of the company but shortly afterwards he was approached by an emissary of the newly elected President Kennedy and, at considerable financial sacrifice, he abandoned his career in industry to become Secretary of Defence.

The task he faced was complex and difficult. His Republican predecessors had superimposed new layers of bureaucracy on the intact civilian departments controlling the three services, each of which jealously managed its own budget, procured its own weapons systems and designed its own strategy. One could almost say that each was preparing for its own different war; certainly each was building its own missile system.

McNamara’s term at the Pentagon was distinguished by three great achievements. He established the supremacy of the civilian Secretary, not only over the civilian bureaucracy, but also over the military. He streamlined and organised the budgetary and procurement systems, not hesitating to prune back favourite programmes. His most decisive contribution was the way he radically altered American strategic thinking, and then provided the forces to make the new strategy credible.

The rigidities of official nuclear doctrine had been under attack for some time in intellectual circles. Academic thinkers about strategy, such as Herman Kahn, Thomas Schelling and Henry Kissinger had been refining the techniques of strategic analysis. McNamara mastered the corpus of their writings, whose mathematical logic was akin to his own habits of thought.