Who is Robert McNamara from Thirteen Days; a Memoir of the Cuban Missile Crisis and what is their importance?

The U.S. Secretary of Defense in the Kennedy Administration, McNamara is, according to RFK, considered by the President the most valuable person in government. McNamara strongly advocates blockade as flexible, dramatic, forceful, and controllable, while "surgical air strikes" on missile bases alone are impractical. If an invasion is needed, McNamara reports confidentially and is approved by JFK, a 90,000-man elite invasion force will grow to 250,000 ground troops where 2,000 air sorties will be flown, and 25,000 casualties can be expected. Worse, McNamara foresees nuclear holocaust and frames the issue in terms that JFK finds appropriate.