Moosburg, along with several of his colleagues, including Johannes Marquart, where he remained until June 1946 without being interrogated about his work. When he left the internment camp, Pietsch returned to work as an editor, gaining employment at the Jahrbuch über die Fortschritte der Mathematik and the East German Academy of Sciences in East Germany, and he maintained these positions until he died in 1967. Case Wicher After the Invasion of Poland, Pietsch, along with another cryptanalyst, Walter Fricke, interviewed a group of captured Polish cryptanalysts to ascertain whether the Polish cryptographic agency had managed to cryptanalyse the Enigma. The subsequent interviews and the whole wartime episode became known as Case Wicher. and rested upon the discovery of a solved Enigma message that had been discovered in the Cryptanalytic Bureau Wicher organisation in Warsaw, Poland in 1939. This was an Enigma message that had been transmitted from a German cruiser in Spanish waters during the Spanish Civil War and had been transmitted using the officers cipher. Pietsch along with Bohm and Steinberg played an important role in conducting security studies into the Enigma that resulted from Case Wicher in the years that followed the discovery of the solved message. Two specific instances of studies leading to action were demonstrated. The first was the discovery that double encipherment of the indicator was a serious insecurity in the use of the Enigma. As a result, on 1 May 1940, nine days before the beginning of the western campaign, in army and air force, the key procedure was radically changed for the Army and Luftwaffe Enigma machines. The second in 1944 was when Pietsch recommended that the Enigma daily use should be set below 20000 letters of use a day. Bibliography See also Secret operation Wicher References 1907 births 1967 deaths German cryptographers 20th-century German mathematicians