Ludwig Föppl

Karl Ludwig Föppl (27 February 1887 – 13 May 1976) was a German mechanical engineer who succeeded his father, August Föppl as professor of technical mechanics at the Technical University of Munich. During World War I, Föppl worked as a cryptanalyst, initially in Inspectorate 7/VI, and later in the war within General der Nachrichtenaufklärung.

By 1940, he was a full member of the Bavarian Academy of Sciences. Föppl was one of the earliest cryptoanalysts in the Germany Army, working at this profession during both the first and second world wars, eventually becoming Chief of Sixth Army’s Evaluation Office. His work was kept secret from both his family and his colleagues, even his later university assistant Friedrich L. Bauer, who would also become a well known cryptologist in his own right, never knew. In 2005, the work of Hilmar-Detlef Brückner of the Bavarian State Archive (German: Bayerisches Hauptstaatsarchiv) brought this aspect of Föppl's career to prominence. Brückner's work was subsequently fleshed out from information contained in Föppl's unpublished autobiography, still retained by his family, several chapters of which provided details of his work during the two world wars.