In the same year he defended his Ph.D. dissertation in history which he made under the direction of from 1922--1927, in Düsseldorf from 1927--1930 and then in Königsberg from 1930--1935.
In the same year he defended his Ph.D. dissertation in history. He began his career as an archivist in Berlin from 1922--1927, in Düsseldorf from 1927--1930 and then in Königsberg from 1930--1935.