Hans Karl Georg Heinrich Pietsch (22 November 1907 – 14 October 1967) was a German mathematician who was most notable for being a director of the Mathematical Referat of the Wehrmacht signals intelligence agency, the General der Nachrichtenaufklärung during World War II. Life In 1938, Pietsch was promoted to Dr Phil with a doctoral dissertation titled: Areas that have a bundle of closed geodesic or a pair of conjugated counterparts (German:Über Flächen, die ein Bündel geschlossener Geodätischer oder ein Paar konjugierter Gegenpunkte besitzen), achieving a rerum naturalium at Humboldt University of Berlin. His doctoral advisor was Ludwig Bieberbach, the mathematician and nazi. Career In 1930 Pietsch was appointed to the mathematical review journal, Jahrbuch über die Fortschritte der Mathematik and held the position until the start of World War II. On 22 November 1939, Pietsch was conscripted into the Wehrmacht as a mathematician and was ordered to report to Inspectorate 7/VI (abbr. Insp 7/IV), the signals intelligence agency Wehrmacht with the rank of specialist. Pietsch was assigned to the Army Signal Security Agency Referat IV of Insp 7/IV along with about a dozen other mathematicians that included several actuarial mathematicians. This included the mathematicians Herbert von Denffer, Friedrich Böhm and Hans-Peter Luzius. Referat IV dealt with analytical research, specifically security of own process and this included distribution of keys and security of the Enigma and security of hand ciphers and associated procedures. By late 1940, the organisational layout of Inspectorate 7/VI was found insufficient to handle the ever-increasing amounts of intercept traffic and a plan was formulated to reorganise the unit. In January 1941, the new unit, called Inspectorate 7/VI, became operational. Pietsch was assigned to both Referat 1 as deputy director with Steinberg as director and Referat 7 with Pietsch as deputy director with Friedrich Böhm as director. On 1 October 1941, Pietsch was promoted to Special leader () and then, on 1 April 1942, to Staff Sargeant () and left the German army with the rank of Baurat, a senior service rank in the German civil service. At the end of 1942, all the Referats were combined into two super Referats or Hauptreferats with the first one being called A for languages that was directed by Rudolf Bailovic and the second Hauptreferats B for the mathematical section that was directed by Pietsch. At the end of the war, Pietsch was interned at Civilian Internment Camp No. 6 in