Early friend and exponent of German Expressionist artists, taught art history at the Bauhaus. He was born in Karlsbad, Bohemia, which is present-day Karlovy Vary, Czech Republic. Adler was born to Therese (née Hirsch) and Mortiz Adler, both of Jewish descent. Adler’s father was a theater critic and socialist. Adler lived in Munich from 1917 onward, where he wrote his dissertation at that university the same year. His topic was the early development of the woodcut. In Munich he became familiar with the Blauen Reiter artists group and for whom he worked.