At the age of 87, Robert S. McNamara, U.S. Secretary of Defense from 1961-1968, sits to be interviewed by documentary maker Errol Morris. McNamara presided over such defining events in American history as the Bay of Pigs, the Cuban Missile Crisis, and the Vietnam War. To this day, he is one of the most controversial figures in U.S. history. In this film, the former politician discusses the various difficult lessons he learned about the nature and conduct of modern war.