After deployment on the Italian Front at Isonzo , he was granted study leave, which he used to start studying law at Vienna University. There he also attended the lectures of Wilhelm Jerusalem. At the beginning of 1918 he was accepted in Schönberg's composition seminar. With Schönberg he studied the theory of form, counterpoint and orchestration. Ullmann was an excellent pianist, although he had no ambitions for a career as a soloist.