Enigma and the Government Code and Cypher School to 1939

LINKS to other pages in the Bletchley Park site and to the 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:

SHORTLY AFTER the outbreak of the First World War the then First Lord of the Admiralty, Winston Churchill, appointed Sir Alfred Ewing, the Navy's Director of Education, to lead the naval code breakers' section then located in Room 40 of the old Admiralty buildings. Ewing not only set up radio listening stations around the country but also recruited several language experts from the Dartmouth and Osborne naval colleges. One of the first of these naval instructors turned code breaker was a Scot, Alastair Denniston, who later became the first head of Bletchley Park.

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      ALASTAIR DENNISTON (left) in London during the war.
      DENNISTON'S OFFICE (below-right) at Bletchley was situated on the ground
      floor of the mansion and under the large copper dome that
      has turned green following exposure to the elements.
      Hut 4 can be seen on the left in the background.

   The most fruitful source of code breakers, however, was the universities. Ewing selected Dilly Knox and Frank Birch from his old college, King’s, in Cambridge. Others included the lawyer, William 'Nobby' Clarke, and publisher, Nigel de Grey. (De Grey’s effort provided for Room 40 its greatest First World War coup, the deciphering of the Zimmerman Telegram.)

   During the First World War, there had been great rivalry between Room 40 and MI1b with little or no collaboration on code breaking, merely on the results. At end of the war Room 40 and MI1B were amalgamated into one as the Government Code and Cypher School (GC&CS) which was run by Alastair Denniston under Admiral Hugh Sinclair who at the time was Director of Naval Intelligence and later (1923 until his death on 4 November 1939) head of MI6. Its published duty was to advise the government on the codes and cyphers it should use. However its main purpose was covertly to decode the secret messages being sent into and out of other countries, both friends and foes.

   During the 1920s, a coding machine named ‘Enigma’ was being marketed by Arthur Scherbius (born in Germany in 1878 and later became a Berlin electrical engineer ) who had invented it in 1918. Originally marketed to the German industrial and banking sectors to prevent their professional secrets being compromised in the normal public telegraph system, the machine was not a commercial success. The internal set-up of the machine was complicated to the degree that it was considered impossible for an outsider to unravel the coded messages that it produced. And yet its operation was so simple that virtually anyone was capable or putting messages into code.

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   However, the German armed forces were becoming increasingly aware of the value of radio communication in warfare. Then, in 1925, the Reichswehr (German Army) tested some of the machines and eventually bought over 30,000. The machines used by the military and other government organisations (such as the railways) had different internal wiring from that of the few commercial machines that had been sold, and the German Navy made even more changes which further increased the security of their machines. Adapted for military use, the machine proved to be of great value particularly because of its ease of operation even under severe battle conditions.

   After Hitler’s rise to power in 1933 ‘Enigma’ became widely used in the German armed forces – a fact noted by the British who, like the Germans, at the time regarded the codes as unbreakable.

   However, in the summer of 1936 BletchleyTuring.jpg - 44988 BytesDenniston asked Dilly Knox to try and solve the riddle of the Enigma coding and early in 1939 Peter Twinn, a mathematician from Brasenose College, Oxford, joined the team to assist Knox. But success eluded them. In late 1939, another mathematician joined the Bletchley team.
Alan Turing (pictured left) was a fellow of King's College, Cambridge. This shy, personally untidy man in his late twenties was, nevertheless, a true genius. At the age of twenty-four, he had developed the theory of a machine which later formed the basis of the modern computer.......

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ALAN TURING, while at Cambridge, rowed for King's College, Cambridge. (Right)

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