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).
After a homosexual episode on a train in 1940, Welles's political enemies used it against him and, threatening a Senate investigation, forced Roosevelt to accept his resignation in 1943.
Welles was born into wealth and privilege, with a family prominent in society. He preferred to be called Sumner after his famous relative Charles Sumner, a leading Senator in the Civil War and Reconstruction. Welles was a grandnephew of Caroline Schermerhorn Astor. A sister of his paternal grandmother, Katherine Schermerhorn Welles, the high society, manners and rules of Mrs. William Astor's New York was dramatized by author Edith Wharton in The House of Mirth (1905) and The Age of Innocence (1920).
At the age of 10, Welles was entered in Miss Kearny's Day School for Boys on 42nd Street, between Fifth and Sixth Avenues. In September 1904, a month before he turned 12, he entered Groton School in Massachusetts, where he remained for the next six years.
Welles then attended Harvard College, where he was a top student, graduating in 1914. Following the advice of Franklin Roosevelt, he went into the Foreign Service and won an assignment to Tokyo, Japan, where he was third secretary at the U.S. Embassy
He and Esther "Hope" Slater were married on April 14, 1915, in Webster, Massachusetts, with the reception being held in Boston. They had two sons, Benjamin Welles (1916-2002), a foreign correspondent for the New York Times and author of his father's biography, and Arnold Welles (1918-2002). They were divorced in Paris in 1923.
He was married on June 27, 1925, in New York City, to Mathilde Townsend. She was a wealthy Washington, D.C., socialite whose first marriage (1910-1924), which ended in divorce, had been to Peter G. Gerry. Welles and Townsend's marriage ended with her death in 1949. She left him $200,000 in her will.
He was married for a third and final time on January 8, 1952, in New York City, to Harriette Appleton Post, a childhood friend whose paternal grandfather was architect George B. Post, who designed the New York Stock Exchange. She was married and divorced twice, to R. Thornton Wilson and Baron Emmerich von Jeszenszky, after which she resumed her maiden name.
Welles specialized in Latin America, was sent to Argentina in 1919, became fluent in Spanish, and proved a quick study in grasping the complexities of Latin American politics. In 1920, he became assistant chief of the Division of Latin American Affairs in Washington, and focused his attention on the Caribbean and Central America. He monitored closely the situations in Cuba and Haiti (then under American occupation).
In 1922, Welles briefly resigned from the State Department, upset with Republican high tariff policies and the inefficiencies of the bureaucracy. The Secretary of State, Charles Evans Hughes, brought him back as a special commissioner to the Dominican Republic with the rank of minister and with direct access to the secretary. Welles remained in this post for three years, but failed to end American control of the nation's economy or to bring about the withdrawal of American troops there.
Welles promised President Gerardo Machado help of new commercial treaty to relieve economic distress if Machado reached a political settlement with the opposition. The government believed that the proposed mediation represented a clever form of continued support and a guarantee that Machado would serve a full length of his term.
Welles promised the opponents of Machado’s government a change of government, and participation in the subsequent administration, if they joined the mediation and supported an orderly transfer of power. The opposition believed that the mediation was an ingenious method by which the United States planned to remove Machado.
The mediation provided the United States the means with which to pursue several policy objectives at once. The mediations provided the means through which opposition groups could obtain their objectives and join the political process in an orderly, instructional fashion. Just as important as easing Machado out was the necessity of easing new political elements in. The mediation conferred on sectors of outlawed opposition a measure of political legitimacy, providing them with a vested interest in a settlement sanctioned and supported by the U.S. This served as a recruitment process, a method by which the U.S. determined which groups were "responsible" and which were not.
Not being able to influence Machado, Welles negotiated an end to his presidency, with support from General Herrera, Colonels Castillo and Delgado, et cetera (See Hugh Thomas ISBN 0-306-80827-7 and Enrique Ros). Fulgencio Batista, an army sergeant in the Cuban Army Telegraph service was still not a player. In September 1933, Batista emerged on the public scene a leader of an enlisted man rebellion, and began to seize control. In January 1934, Batista transferred army support from Ramón Grau to Union Nacionalista leader Carlos Mendieta. Within five days, the United States recognized the new government.
Roosevelt was embittered by the attack on his friend, believing they were ruining a good man, but was forced to accept Welles' resignation in 1943.