Prawer found that he was unhappy with mathematics, and his father suggested he study history instead since he had always enjoyed history in high school. His professor, Richard Koebner, an Anglophile historian of imperialism, set him on the course of studying the crusader colonies in the Holy Land. The close ties to Koebner were likely to have instilled in Prawer his interest in the history of settlements and colonialization. Prawer began his teaching career at the Hebrew University in 1947 and (after fighting in the 1948 siege of Jerusalem) soon rose through the faculty ranks. He became deputy dean of the Faculty of Humanities from 1953 to 1955, was made professor and chair of medieval history in 1958, was dean of the Faculty of Humanities from 1962 to 1966, and served as prorector at the university in the years 1975–78. In the process, he succeeded in making the university into a "global center" for Crusade Studies, and trained many future Israeli historians in that specialty. Prawer has been described as an outstanding teacher and lecturer who combined thorough preparation with a charismatic style. He was often invited to lecture abroad.
