McNamara is a bit of an enigma. Fog of War more or less allowed him to speak and what we got was not necessarily an objective examination of the man and his role, but rather the equally interesting- though historically subjective- perspective of how McNamara saw himself.

McNamara was a technocrat: give him enough data and he could crunch the numbers and tell you how to do things: how to bomb German industry, how to make thousands of Chevrolets efficiently.

What he could not tell you was how to break the will of a peasant people seeking independence and to emerge from colonial subjugation to take their place in the world. Because that's not something amenable to data, spreadsheets, and cost-benefit analyses.

McNamara's recommendations changed over time. It is important to bear in mind that he was appointed by Kennedy, who had great self-confidence and grew into the presidency. He could filter McNamara's ultra-rationalism with his intuition and subjective instincts.This is not to say Kennedy was a genius, but that he was willing to take this balanced approach.

Johnson was a different man, perhaps in a sense catching up with the times. He was more the Washington operator and fixer, susceptible to rolling over when confronted by men who had all the answers, and all the data to back them up. McNamara was guilty of constantly proposing 'solutions' to stop the communist/nationalist Vietnamese. The whole administration laboured under the delusion that the Vietnam was was directed by Beijing and/or Moscow and with enough force the Chinese/Russians would desist, just as the US later did in the South. But North Vietnam was not South Vietnam, it had a legitimacy and already had experience of years of struggle against strong opponents.

McNamara's grand failure, and one of which he remained oblivious, was his inability to see the limitations of his over-technical, rationalist approach. He was an ideal man to run a car factory. He was a disaster as a leader in war (which is what he was, even if he preferred to pretend he was more an advisor and others did the leadership).

Rumsfeld repeated his folly almost exactly, though with much more mendacious motivations.