Welles, Sumner, 1892–1961, American diplomat, b. New York City. Welles began his diplomatic career as secretary of the U.S. embassy at Tokyo (1915–17). Attached to the embassy at Buenos Aires (1917–19), he then served as assistant chief (1920–21) and chief (1921–22) of the division of Latin American affairs of the Dept. of State. As commissioner to the Dominican Republic in 1922, he helped prepare for the evacuation of American troops from that country; later he was sent to offer mediation in the Honduras revolution of 1924. He wrote a book on the Dominican Republic, Naboth's Vineyard (1928), and was an influential member of the Dawes financial mission to the Dominican Republic (1929).
President Franklin Delano Roosevelt appointed him assistant secretary of state in 1933 and in the same year sent him as ambassador to Cuba. There he was unable to bring about successful mediation between the opposing groups in the revolution against Gerardo Machado in 1933, and in the midst of political turmoil he was recalled and resumed his duties as assistant secretary of state. He later (1937–42) was undersecretary of state and served as U.S. delegate to several Pan-American conferences. In 1940 he went on a confidential fact-finding mission to Europe, and he took part in the meeting at sea between Roosevelt and Winston Churchill that produced the Atlantic Charter (1941). He resigned from public service in 1943. Some of his speeches were collected in The World of the Four Freedoms (1943); his other writings include The Time of Decision (1944), The Intelligent American's Guide to Peace (1945), Where Are We Heading? (1946), and Seven Decisions That Shaped History (1950).
See biography by his son B. Welles (1997).