Wilhelm Fenner (14 April 1891 in Saint Petersburg, 25 July 1961 in Bad Godesberg)[1][2] 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).

[3] 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.

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.

[5] The fledgling news agency collapsed, with Krusenstern relocating to Paris, but before he left, Fenner's career took a decisive turn when the Russian colonel introduced him to Peter Novopaschenny in the spring of 1921.

In 1919, Buschenhagen had set up Volunteer Evaluation Post which had been absorbed into Germany's postwar military establishment as a cipher bureau of the army's Troops Department, which was allowed under the terms of the peace agreement.

Fenner was initially unimpressed by the cipher bureau personnel, output was modest with too narrow scope of operation, and cryptanalysts happy to decrypt three or four messages a day combined with lax work habits.

In this process, Fenner introduced a uniform, clear technical terminology into the field of cryptanalysis, laying the groundwork for further successes by his new employer.

However, his growing leadership role caused him to start losing contact with the actual cryptanalytic work, and gained a reputation as a fearsome, arrogant pedant, which he dismissed as evidence the unit was being shaken out of its lethargy.

[6] In addition to his management duties he increased contact and cooperation with friendly foreign groups in Austria, Hungary and Finland,[7] and later Italy, Spain and Estonia[8] 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).

[5] Specifically, he promised Selchow that as the OKW/Chi expanded and improved its radio monitoring network, the foreign ministry cryptanalysts would have access to all diplomatic messages intercepted.

[5] Fenner had little patience with these people, who talked politics during extended coffee breaks and who flaunted their loyalties by smoking Nazi Party cigarettes, or occasionally missed work to participate in a Jew raid.

[5] After the seizure of power by the Nazis in January 1933, the times became increasingly restless, and the situation worsened for the cipher bureau, which now felt the competition from newly established rival institutions.

Reznicek was particularly annoyed that in the caste conscious world of German bureaucracy, he was a mere employee of the Bureau, while Fenner was a Government Councillor with a pensioner.

[9] 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.

From either a desire to revenge themselves on their former employer or to expand their influence, Schimpf and Schapper informed Fenner that the Forschungsamt was now solely responsible for all diplomatic cryptanalysis and that the Bureau should abandon all such work.

[5] This was of course a repeat of the last bureaucratic battle with the Pers Z S. However, Fenner found an ally in Kurt Selchow, who realized that if successfully prosecuted, the Forschungsamt's supposed monopoly on diplomatic cryptanalysis would mean the end of the Foreign Ministry.

[5] Fenner was forced to fill the resulting gaps with newcomers, necessarily having to forgo experience in favour of attitude in selection of candidates.

[13] 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.