Chayes was born on July 18, 1922, in Chicago. He received his A.B. magna cum laude from Harvard in 1943. From 1943 to 1946 he served with the field artillery in France, Holland, Germany, and Japan. He was discharged with the rank of captain and returned to Harvard. He received his LL.B. magna cum laude from Harvard Law School in 1949. He served as note editor and then president of the Harvard Law Review. After law school, Chayes served as legal advisor to Gov. Chester Bowles of Connecticut from 1949 to 1951. He then went to Washington, D.C., serving as associate general counsel of the President's Materials Policy Commission in 1951, as a clerk for Justice Felix Frankfurter of the U.S. Supreme Court from 1951 to 1952, and as an associate with Covington & Burling in Washington, D.C., from 1952 to 1955. Chayes returned to Cambridge in 1955 to join the Law School faculty as an assistant professor, becoming a professor of law in 1958. Chayes was one of the initial group of Harvard faculty members who worked in the late l950s on President Kennedy's campaign. He was the head staff person and lead draftsman of the l960 Democratic Convention platform, and during the fall of 1960 was one of the principal issues advisers to the Kennedy campaign. In 1961, Chayes played a major role in the development of the United States' position in the Berlin Crisis of 1961, the Cuban Missile Crisis of 1962, the Limited Test Ban Treaty of l963 (which banned atmospheric nuclear tests), and the establishment of Comsat (the Communications Satellite system).Chayes came back to the Law School in 1965. In 1976, he became the Felix Frankfurter Professor of Law, and in 1993, he became the Felix Frankfurter Professor of Law, Emeritus.After Chayes returned to Harvard Law School, he continued his work in international affairs. In l972 Chayes was one of the principal foreign policy advisers to the presidential campaign of Sen. George McGovern, and in l976 he was a foreign policy adviser to the presidential campaign of Gov. Jimmy Carter.In the l980s, Chayes continued to spend considerable time on international law issues, ranging from Cold War questions to environmental and communications matters.