The Enigma Busting Bombe Machine


The bombe project began at Bletchley Park in 1940 in a modest way, with just three people, representing the three Armed Services. The original principles of the bombe machine, used to find the secret settings of the German Enigma cipher machine, was thought up by the Cambridge mathematician Alan Turing, and later improved on by another mathematician from Cambridge, Gordon Welchman. The machines were built by the British Tabulating Machine Company (BTM) at Letchworth in Hertfordshire, led by Harold ‘Doc’ Keen.

The first Enigma busting bombe machine came into operation at Bletchley Park on 14 March 1940 when the unit was working in half of Hut 1, the other half comprising the sick bay! The entire bombe unit was crammed into an area 15 feet by 12 feet, which was, on occasion, also the dining room and sleeping quarters.

Besides this first machine –dubbed ‘Victory’ – there was also a ‘baby’ known as ‘The Test Plate’, but with the arrival of Victory, this machine took second place. Victory was only out of action 42 hours in the first 14 months, during which time extra innovations and modifications were added. At first all the work of Victory was for the naval codebreaking section in Hut 8, and an improved version, Machine No 2, known as ‘Agnus’ or ‘Agnes’ – affectionately known as ‘Aggie’ – came on stream on 8 August 1940.

(C) John Jackson

In 1941 it was decided to increase the number of bombes and to employ Wrens as operators, leaving the men to look after the machines. For security reasons it was decided to send machines to out-stations, the first being at Wavendon a few miles from Bletchley Park, where Victory was sent after being fitted with the diagonal board. By the end of March 1941, another machine had been delivered which was the first to be fitted with an automatic typewriter to print and check stops, known as a ‘Jumbo’. Later typewriter machines were all known as Jumbo-type.

Eight Wrens arrived on 24 March 1941 and with an increase in staff and bombes, another outstation, at Adstock, also near Bletchley Park, was opened that month. At the same time the Section moved from Hut 1 to Hut 11. During the life of the Section, nearly 3,000 Wrens were trained. The requested establishment later on was for 1,850 Wrens and 275 men to operate and maintain 202 machines. By the end of 1941, there were 16 machines in operation, six in Hut 11 and five each at Adstock and Wavendon.

In February 1942 a new building, Hut 11a, was completed next to Hut 11, which remained for office purposes but was later given up to another administration section. That month saw the addition of two more bombes. With the Section’s growth a room was set aside fitted with telephones to Hut 8 (Navy codebreaking) and Hut 6 (Army and Air Force codebreaking), as well as to Adstock and Wavendon. By the end of March 1942, there were 26 bombes in operation and in September a third outstation was opened at Gayhurst, also a few miles from Bletchley Park. The same month Victory was removed from operational work but was kept for experimental and instructional purposes to the end of the war.

On 6 November 1942 a new type of bombe machine arrived, which handled German Secret Service (Abwehr) Enigma-enciphered messages. It was installed in Hut 11a and ran a completely different type of menu from the other machines and was known as ‘Funf’ after a popular comedy character in the famous BBC radio show ITMA – It’s That Man Again –which starred Tommy Handley. The name was derived from fünf, the German for five. By the end of 1942 a major new outstation was built at Stanmore in Middlesex, consisting of 10 large bays, each as big as Hut 11a, and was operational by November. At the end of 1942, there were 49 bombes in action.

(C) John Jackson

By early 1943, the mechanical times for bombes to complete a run was 16 minutes. March 1943 saw the first of the high-speed Keen four-wheel machines to attack messages sent on the four-wheel Enigma U-Boat networks, and was delivered to Stanmore.

There was another type of high-speed four-wheel machine, which had been in use since August 1942, devised by Dr Charles Wynne-Williams of the Telecommunications Research Establishment, run and maintained by GPO engineers, but was more experimental than operational. In March 1943, the first bombe of this type was delivered to Stanmore. In addition there were ordinary three-wheel bombes with a high-speed fourth wheel attachment known as the ‘Cobra’, installed in two specially fitted bays at a new outstation at Eastcote, in north London, with 12 bays, which commenced in September 1943, although it was not officially opened until early 1944.

On 31 January 1944, the first of a new type of machine was installed at Eastcote, fitted with Siemens BTM relays. In March 1944, a special American bay was set up at Eastcote comprising 10 machines, run entirely by personnel of the 6812th Signal Security Detachment, US Army. During their operations, this unit solved 425 Enigma keys.

In June 1944 an experiment was conducted to couple together, electrically and mechanically, four three-wheel Bombes, known as a ‘Giant’. However, further discoveries and developments made it obsolete, because greater speed was necessary to produce the required results. Therefore, the same principles were applied to four High-Speed machines, known as the ‘Ogre’, but the urgency for its use arose before it had left the experimental stage at BTM, and it commenced operations there. It was never delivered to the Section, whilst Giant was separated and run as four ordinary bombes. These machines never became part of the work of the Section. By the end of 1944 there were 192 machines operational.

The war ended on 8 May, 1945 and on this date all the bombe machines stopped running – the first since commencement of operations in 1940 and dismantling began the next day. However, it was decided to keep a few bombes running for research etc., and to retain 50 machines of various types, overhauled and stored away. The work of three machines for the Abwehr Section continued for some time after VE Day, but they, too, eventually stopped work. When World War Two ended in Europe, the number of people involved with the bombe project was 263 men – mostly RAF – and 1,676 women – all WRNS. In all, there were 211 machines. In addition, the Americans had built 121 four-wheel machines for U-Boat traffic at the National Cash Register Company at Dayton, Ohio.

However, work did not completely stop even with the surrender of Japan in August 1945. Eastcote was the first outstation to be completely cleared. It was decided to recommence some operational work (the nature of which is even today unknown), and 16 bombes came back into action.

Instead of keeping Stanmore open, Eastcote was reopened and the bombe machines all had to be moved once more, from Stanmore to Eastcote. Some were to be stored away but others were required to run new jobs and 16 machines were kept comparatively busy on menus.

Interestingly, most of the post-war jobs came up, and the operating, checking and other times maintained were faster than the best times produced during the war! During this period the staff was reduced considerably, all the Wrens left the Section and the RAF personnel were reduced to 80 to finish dismantling, operating and disposal of scrap material. The Section was finally wound up at the end of 1945.

This article, The Enigma Busting Bombe Machine has been prepared by John Jackson. John Jackson retains the copyright to the words and the photographs. Any reference to the material contained therein should be credited to him and Bletchley Park Research. If you would like to contact John or learn more about Bletchley Park Research then please, Subscribe to our newsletter.

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