After the war Dupuy returned to the
War Department's Bureau of Public Relations, serving as its acting director until his retirement, as a
colonel, in May 1946. His military honors include two awards of the
Legion of Merit. Dupuy was a military historian and had written a number of books in the inter-war years during his spare time. He returned to this passion in retirement and wrote 100 articles and short stories, as well as 22 published books. Dupuy also served as an associate editor of the
Army-Navy-Air Force Journal for five years and was a director and staff editor of the
Historical Evaluation and Research Organization (HERO) from 1963. In March 1966, he was inducted as an honorary member of the U.S. Military Academy Class of 1913. In their later years, Dupuy and his wife lived in
Arlington, Virginia. He died on April 25, 1975, at the
Walter Reed Army Medical Center, Washington, D.C. == Publications ==