In 1997, Hughes received the American Historical Association's Award for Scholarly Distinction, given to historians of "the highest distinction." He was also commended by the Italian government for his work in Italian history.

Hughes was not only a noted intellectual--he was also revered for his activism.

Alongside Dr. Benjamin M. Spock, Hughes co-chaired the National Committee for a Sane Nuclear Policy (SANE), a group worried about the massive worldwide nuclear arms buildup during the Cold War and nuclear weapon testing.

The group warned the public in a 1962 full-page New York Times advertisement that nuclear radiation was appearing in American mother's breast milk, posing a major danger for children.

On a pro-disarmament platform, Hughes ran in Massachusetts as an independent candidate for U.S. Senate in the 1962 race against Democrat Edward M. Kennedy '54-'56.

In 1967, Hughes became chair of SANE, a position which he held until 1970.

Hoffmann, who called Hughes a beatnik, said Hughes was one of the few Harvard professors to publicly object to the war.

Hughes' action against the war was deliberate and well-thought-out, according to Hoffman; for example, he did not support the students' actions of disrupting classes.