University of Vienna Byzantinist and San Marco scholar. Demus's father, Carl Demus, was a physician. His father was killed early during the First World War and the younger Demus partially supported of his family as an adolescent. He entered the University of Vienna in 1921 during the time of the historic (and bitter) split between the faculty of Josef Rudolf Thomas Strzygowski, and Julius Alwin von Schlosser. The rivalry between these two men was such that studying with both was impossible.