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Royal Naval Museum

The Enigma Machine


A new display case exhibiting the enigma machine is now in the foyer of the Main Museum Building.

Nazi U-boat (submarine) Enigma Machine, M15653

Four rotor or M4 Enigma machine, issued to Nazi U-boats in the Atlantic and Mediterranean, from 1942 onwards.

Until 1941, Enigma machines were made with only three rotor slots. The addition of a fourth rotor slot made Enigma code even more difficult to crack.

All Enigma machines carried up to eight different rotors that the operator could choose from. The rotors could be removed from the Enigma and re-fitted, in any position. Although the new fourth rotor (named BETA), was not interchangeable with any of the other eight.

Allied crews were told that the most important part of the Enigma was its rotors. If at all possible, they should try to capture them from an enemy ship. This was not easy as the rotors were locked into the machine!

This Enigma machine contains rotors I, V, II and IV out of the possible eight.

Donated by HMS Mercury, the Royal Navy Signal School, based at Leydene, near Petersfield, Hampshire.




The M4 Enigma, HMS Petard and U559, 30th October 1942

On 30th October 1942, the naval destroyers Petard, Pakenham, Hero, Dulverton and Herworth attacked the Nazi U-boat U559, off Port Said, Egypt.

After nearly ten hours under attack, U559 was forced to surface and the Captain told his crew to abandon the submarine.

Lieutenant Anthony Fasson, AB Colin Grazier and canteen assistant, Tommy Brown (aged 16) of HMS Petard, swam out to the stricken U-boat. They were to search for secret code documents and an Enigma machine. They were joined by Lieutenant Spens-Black, AB Kenneth Lacroix and AB G W McFarlane.

The boarding party found code books which were passed back to the Petard and also an Enigma machine. The Enigma machine disappeared into the water as the U-boat began to sink. Sadly, Lieutenant Fasson and AB Grazier drowned.

Their bravery in recovering the code books enabled the code-breakers at Bletchley Park to break the M4 cipher. After ten months of not being able to read Nazi messages, the cipher (know as Triton) was broken.

Lieutenant Anthony Fasson and AB Colin Grazier received the George Cross. Canteen assistant, Tommy Brown received the George Medal.

[Rebekah Moran, Education Officer - 12 September 2000]

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Created on the 12 September 2000