In November 1923 he married Ilse Siefert, with whom he had four children. He was appointed parish priest in Mecklenburg. In 1928 he went to Colombia and Ecuador. In 1930, in Guatemala, he supported a local evangelical community; a year later he joined the NSDAP and founded the first Nazi group abroad.
He served as the representative of German government in Montevideo, Uruguay (1937-1942) during the Battle of the River Plate in 1939. He held that position until the Uruguayan government broke off relations with Germany.
- Deutsche Christenheit in der Zeitenwende. Hamburg, Agentur des Rauen Hauses 1933. 77 pages
- Walter Birnbaum: Zeuge meiner Zeit. Aussagen zu 1912 bis 1972. Musterschmidt, Göttingen 1973, ISBN 3-7881-1675-7
- In: Die Deutschen in Guatemala 1930-194, 30 November 2009, Ein Pfarrer für Guatemala
- Actual Rupture Is Left to Congress of Each Signatory. In: The New York Times. 22 January 1942, Unanimous agreement by the twenty-one American republics on a resolution for severance of relations with the Axis powers was reached late today at a three-hour consultation in the office of Foreign Minister Oswaldo Aranha of Brazil, who is chairman of the Inter-American Conference.
- Uruguay, Peru Break Relations with Axis. In: Chicago Tribune. 25 January 1942, Uruguay and Peru severed diplomatic relations tonight with Germany, Italy, and Japan. putting into swift effect terms of a compromise anti-axis agreement ...