Wilhelm Fenner

Wilhelm Fenner (14 April 189125 July 1961) was a German cryptanalyst, before and during the time of World War II in the OKW/Chi, the Cipher Department of the High Command of the Wehrmacht, working within the main cryptanalysis group, and entrusted with deciphering enemy message traffic (Cryptography). Wilhelm Fenner was considered an excellent organizer, an anti-Nazi, an anti-Bolshevik and a confirmed Protestant and was known by colleagues as someone who was keen to continue working in cryptology after World War II. To quote military historian David Alvarez:

Wilhelm Fenner was the central figure in the evolution of the German Cipher Bureau between 1922 and 1939, and a major personality in the history of German communications intelligence in the interwar period. Under his direction, the Cipher Bureau evolved into a highly professional communications intelligence service, which scored impressive cryptanalytic successes against the diplomatic and military systems of many countries.

Personal life Wilhelm Fenner was born on 14 April 1891 in Saint Petersburg. He was the sixth of seven children of Heinrich Gottlieb Fenner and Charlotte Georgine Fenner, née Michaelsen. His father was the chief editor of the St. Petersburgische Zeitung, a German language daily newspaper published in Saint Petersburg, then the capital of the Russian Empire. The sixth of seven children, he was home schooled for two years before he attended the evangelical lutheran Anne School in St. Petersburg from 189. He completed his final examination with distinction in May 1909. In the autumn of 1910, he matriculated at the Royal Institute of Technology in Berlin (TH) in Berlin-Charlottenburg and studied construction engineering, chemistry and metallurgy. In addition to his management duties he increased contact and cooperation with friendly foreign groups in Austria, Hungary and Finland, and later Italy, Spain and Estonia He provided training, and wrote two treatises on cryptanalysis, namely Grundlagen der Entzifferung (fundamentals of code-breaking) and Beitrag zur Theorie der Schieber (contribution to the theory of the strip cipher). He also worked on the Enigma machine, then already in trial use by the Reichswehr, pointing out cryptographic weaknesses, and making proposals for its improvement. By 1924, Fenner had identified in the intercept traffic, 85 codes and ciphers, of which 22 has been attached and 16 had been cryptanalysed successfully. In June 1927, Fenner went to Finland to deliver a course of instruction to the members of the new fledgling service of the Finish cipher bureau. Gottfried Schapper, a radio intelligence operator from World War I, who ran a unit in the Bureau that was concerned with the location and construction of fixed intercept stations.

The staff strength of the Chiffrierstelle (OKW/Chi) had increased in 1939 to include over 200 employees, whereas only two years earlier there were about 40 personnel. In the ensuing war years until 1944 it quadrupled to 800. The wartime for Fenner and his staff in the OKW/Chi was initially relatively peaceful and successful. The raw material, in the form of intercepted radio messages, was prolific; they concentrated on several hundred messages a day on the most important projects and had to ignore relatively unimportant sources. They had important decoding success , for example, against France, in 1940, which aided the quick victory of the German Armed Forces in the West—"Case Red". Also Polish, Russian and Yugoslav messages could be deciphered.

Impact of war While his section chief, Colonel Kettler, and the head of the main group A, Major Mettig, and also one of its best people, the head of the group IV, Dr Erich Hüttenhain, relocated to the north, Fenner fled south with a selection of employees. On 23 April 1945, OKW/Chi was officially disbanded and the staff of the General of Nachrichtenaufklärung (gDNA) assumed their responsibilities. Just before the American army reached their position (about 40 km south of Salzburg), documents were burned or thrown into the Salzach River. With the surrender of the Wehrmacht on 8 May 1945, Fenner moved to Landshut and found employment as a bicycle and car mechanic in neighboring Straubing.

Witness at Nuremberg war crimes trial In July 1946, Fenner was charged as a witness for the Nuremberg war crimes tribunal and in August transferred to the Haus Alaska, a cover name for HQ 7707 European Command Intelligence Center Camp King, the US Army's interrogation centre, Oberursel (near Frankfurt), and interned with other high-ranking Germans. Fenner was intensively interrogated by the Army Security Agency (ASA) and wrote a number of reports about his life and work, including an autobiographical essay "The Career of William Fenner"—its English translation bearing the words TOP SECRET being filed in TICOM Archive: DF-187. These documents were made publicly available in 2008.