The German Naval Codes

LINKS to other pages in the Bletchley Park site and to the Colin Day Travelling Days series:

1 : Bletchley Park Estate to 1939
2 : Enigma and GC&CS.
3 : The Poles and Enigma
4 : Turing and the Bombes
5 : The Huts: An overview
6 : German Naval Codes
7 : Huts 3,4,6 and 8
8 : Blocks A,B,C,D,E and F
9 : Views of the Estate (1)
10 : Views of the Estate (2)
11 : Lorenz and Colossus
12 : Finale, Links, Bibliography
Bletchley Park Guest Book:

WHEN THE BOMBES eventually arrived at Bletchley Park, significant inroads into the German army and air force codes had already made. The Bombes, however, enabled the Enigma settings to be determined more easily, resulting in the decoding process becoming much faster. The German navy codes, however, presented greater difficulties to be overcome.

    An Enigma machine had been recovered from U-33 early in the war. But the Navy had already enforced strict security practices and later added more rotors to their system. Enigma now had eight rotors from which to select the three actually used each day. Without knowing the wiring of all the rotors, few messages could be decoded. In May 1941 a German weather ship, the Munchen, was boarded by the Royal Navy, vital documents obtained and the ship destroyed.

   Soon afterwards the British Navy captured and boarded the German submarine U-110. Its coding equipment was intact. Bletchleyext38a.jpg - 45980 BytesOther material recovered included codebooks, and key listings for various German Navy and submarine codes. The intact Enigma machine, with the daily settings in place, together with its eight rotors. The damaged U-boat eventually sank and the crew taken to Britain and interned for the duration of the war.

The 'mock-up' of a U-boat section as used in the Mick Jagger film, 'Enigma', based on the story by Robert Harris. (Right)

   Admiral Doenitz, the commander of the U-boat fleet, was, however, not convinced by the assurances given to him concerning the security of Enigma following the loss of U-110 and proceeded to change the set-up of U-boat Enigma machines. This involved using four thinner rotor wheels to fit into the space earlier occupied by the three standard wheels. Although Bletchley Park learned of the proposed change from decrypts and other captured material, there was little that could be done until the alterations actually happened. It was indeed fortunate that the other German forces continued, in the main, to use the three rotor system.

   For several months it looked as if Bletchley was going to remain locked out from the German naval codes. However, in October 1942 men from the Royal Navy succeeded in capturing and entering U-559 and recovered vital Enigma machine parts and documents which allowed the code breakers to get back into the German navy’s codes.........

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