An influential twentieth-century historian, he wrote the first detailed account of President Lyndon B. Johnson's decision to de-escalate the Vietnam War. During the late 1960s, he served as Under Secretary of the Air Force.
He attended Yale University, where he was the captain of the football team. He went on to serve in the Marine Corps during World War II.
He is best known for his Bancroft Prize-winning historical book, The Devil and John Foster Dulles (1973).
He was born in Duluth, Minnesota, where his father worked as a Great Lakes steamship executive. His second marriage, to Ann Merrifield, lasted four decades and produced a daughter. Previously, he had been married to Marion Schmidt, with whom he had two sons.
A common topic of Hoopes' writing was the foreign policy of President Dwight Eisenhower.