1962 - Joined the State Department as an assistant to Ambassador Henry Cabot Lodge during the Vietnam War.
1963 - His State Department career included assignments as consul in Saigon.
1964 - 1965 - Vice consul in Hue.
1969 - 1970 - Special assistant to the assistant to the president for National Security Affairs in the Nixon Administration.
1969 - He accompanied National Security Advisor Henry Kissinger on his first secret meeting with North Vietnamese negotiators in Paris.
1970 - He had a falling out with Kissinger over the Nixon administration's extension of the war to Cambodia and later wrote a book critical of Kissinger's approach to Africa.
1974 - He studied economics at Trinity College, Cambridge and later received a PhD from the Woodrow Wilson School of Public and International Affairs at Princeton University.
1977 - Returned to the State Department to serve as Director of Policy Planning for President Carter.
1981 - He withdrew into academia, becoming a professor at Amherst College in Massachusetts.
1984 - He moved to Mount Holyoke College, where he has taught courses on the Vietnam War, Third World revolutions, and American foreign policy.
1992 - He was one of candidate Clinton's chief foreign policy advisers.
1993 - 1997 - He was the National Security Advisor under US President Bill Clinton.
1996 - He was nominated for CIA Director, but his nomination was withdrawn due to Republican opposition.
He is currently a faculty member at the Edmund A. Walsh School of Foreign Service at Georgetown University.