Robert McNamara became the U.S. Secretary of Defense under John F. Kennedy in 1961. He was one of the architects of the Vietnam War. McNamara believed in the Domino Theory. Basically, if one country fell to communism, all of the neighboring countries also would. He helped mislead the U.S. public about the Gulf of Tonkin incident. McNamara intensified the war by drastically increasing U.S. involvement. Later, he lied about the war being unwinnable. He resigned during Lyndon Johnson's administrati