From 1921 until 1935 he held the chair of Pure and Applied Mathematics at the University of Frankfurt but he was forced to leave his post by the Nazi regime in 1938.
Mula 1921 hanggang 1935 siya hawak ang silya ng Ganoon at Applied Mathematics sa University of Frankfurt ngunit siya ay sapilitang sa iwanan ang kanyang post ng Nasi rehimen sa 1938.