His death was announced by Claremont's Harvey Mudd College, where he taught political science for 19 years until his retirement in 2002.
He arrived in Chile in 1971, a year after Allende became Latin America's first democratically elected Marxist president. Davis' term there ended amid suspicions of American involvement in the 1973 military coup that resulted in Allende's violent death, the circumstances of which are still in such dispute that Chile recently ordered the exhumation of his body.
Davis discussed U.S. policy toward Allende's government and refuted allegations of American collusion in its downfall in his 1985 book "The Last Two Years of Salvador Allende."
He was the model for the ambassador in the 1982 Constantin Costa-Gavras film "Missing," which was based on a book of the same name by Thomas Hauser. In 1983, Davis and two other American officials who served with him in Chile sued Hauser, Costa-Gavras and Universal Pictures for libel, alleging that false accusations were made of their complicity in the disappearance and death of American journalist Charles Horman during the coup. The libel suit was ultimately thrown out of court.
Born in Cambridge, Mass., on April 12, 1925, Davis received his degree from Brown University in 1944, the same year he obtained his commission as an ensign in the Navy. He served on the aircraft carrier Lake Champlain until 1946.
A year later, he earned a master's degree from the Fletcher School of Law and Diplomacy at Tufts University. He briefly taught at Fletcher, where he obtained a doctorate in 1960.
Davis joined the Foreign Service in 1947. After serving in Prague, Czechoslovakia (now the Czech Republic); Florence, Italy; Rome; and Moscow, he became a Soviet desk officer for the State Department in 1957. In 1959, he was an escort officer for Nikita Khrushchev when the Soviet leader toured the U.S.
From 1962 to 1965, Davis was a special assistant to Peace Corps director Sargent Shriver and later was a deputy director. He left the agency to take the post of U.S. envoy to Bulgaria in 1965, before America's mission was elevated to an embassy.
Davis was on the senior staff of the National Security Council in August 1968 when terrorists killed John Gordon Mein, U.S. ambassador to Guatemala. Davis was chosen to succeed Mein and served as ambassador during a violent period in that Central American republic before moving on to another delicate assignment, in Chile.
He was named assistant secretary of State for African affairs under Kissinger in 1975, but resigned after four months because of differences with Kissinger and President Ford over covert military operations in Angola. His last foreign posting was as ambassador to Switzerland from 1975 to 1977.
From 1977 to 1983, he taught at the U.S. Naval War College in Newport, R.I.
In a 1986 op-ed piece in the Los Angeles Times, Davis expressed regret that he, "the old fud of an ambassador," had presented "too many shades of gray" in teaching foreign policy to one student in particular. That student was Oliver North, the Marine Corps officer who later made headlines for his role in the Iran-Contra affair.
Davis is survived by his wife, Elizabeth; four children; two sisters; eight grandchildren; and two great-grandchildren.