Former Harvard Gurney Professor of History Henry Stuart Hughes, a leader in the field of European intellectual history and a nuclear disarmament activist, died in San Diego of pneumonia on Thursday. He was 83.

In addition to teaching history at Harvard, Hughes was one of six founders of the Standing Committee on Social Studies in 1960, which created a new concentration to broaden social science students' knowledge beyond narrow specialties.

"When we founded Social Studies, we were looking for people with a breadth of knowledge and Hughes was an obvious choice," said Buttenwieser University Professor Stanley H. Hoffmann, the department's first chair and one of its founders.

Hughes taught at Harvard from 1948 to 1952 and from 1957 to 1975. He left Harvard in 1975 to take a teaching position at the University of California at San Diego, where he became a professor emeritus in 1986.

Hughes was an expert on modern European history, specializing in European intellectual history.

"He was the major intellectual historian of his generation," said Coolidge Professor of History David G. Blackbourn, who teaches European history.

Harvard has been without a tenured professor on European intellectual history since Hughes' departure.

"We in the social studies department regret his death and fondly remember what he did," said Social Studies Department Chair and Government Professor Seyla Benhabib.