Attracted to teaching, he supplied Robert Marichal from 1942 to 1945, then a POW in Germany, to the chair of language and French literature from the Middle Ages at the Institut catholique de Paris. In 1942-1943, he provided locum for Charles Samaran in his Latin and French palaeography conference at the École pratique des hautes études. On 3 November 1949, he was appointed master of conference of medieval history at the Institut Catholique de Paris; He became an assistant professor in 1952 and professor in 1955. Finally, on 1 October 1953 he succeeded Charles Perrat to the chair of history of political, administrative and judicial of France at the École des chartes.
