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The Enigma Machine
The Enigma Machine was invented by the Germans in 1918 solely to encipher and decipher messages.
It consisted of a keyboard of 26 letters in the pattern of the normal German typewriter, but with no keys for numerals or punctuation. Behind the keyboard was a lampboard made up of 26 small circular windows, each bearing a letter in the same pattern as the keyboard, which could light up one at a time. Behind the lampboard is the scrambler unit consisting of a fixed wheel at each end, and a central space for three rotating wheels.
If a key was pressed on the keyboard any other letter could light up, and the sequence would only repeat itself after 16,900 (26x25x26) keyings, when the inner mechanism returned to the same position. Messages were limited to a maximum of 250 letters to avoid this recurrence, which might have otherwise helped the British code-breakers.
Winston Churchill believed that Britain faced no greater threat in World War Two than the havoc wreaked on its trans-Atlantic supply lines by the German U-boat fleet. Without being able to read the codes that the U-boats used to communicate, Allied shipping convoys were in serious and persistent danger.
The first breakthrough came in May 1941, when HMS Bulldog retrieved an enigma machine from crippled U-boat 'U-110'. The Germans later modified the machine, causing a 'blackout' during which Allied codebreakers couldn't crack the Enigma cipher. Allied shipping loses escalated dramatically.
Then in October 1942, 'U-559' was forced to the surface by destroyers 70 miles off Egypt. Three crewmen from HMS Petard boarded the sinking U-boat and seized two vital code books that once again allowed the codebreakers at Bletchley Park to read messages sent by Enigma.
Sadly, two of the men who boarded 'U-559' were drowned when the vessel suddenly sank. First Lieutenant Anthony Fasson and Able Seaman Grazier were posthumously awarded the George Cross. Their sacrifice ensured that the Allies were eventually able to neutralise the U-boat threat.
Presenter Mohini Sule says: "To me the Enigma Machine is the ultimate symbol of the backroom boys’ intelligence work."
Where can it be found? At the Royal Naval Museum, Portsmouth.
Colin White, deputy director, says: "Every time you turn on your computer you are connecting to this machine."
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