On 24th November CARC members were delighted to welcome Dr Brian Oakley, accompanied by his wife Marion, to give a talk “Behind the Scenes at Bletchley Park during WW2”. As a wartime wireless operator Dr Oakley is well qualified in this field, and is a Bletchley Park Trustee, historian and tour guide. He is also a former President of the British Computer Society.
Aware from his military service in South Africa of the importance of secure communications, Winston Churchill as First Lord of the Admiralty created in 1914 the Cryptographic and Intelligence unit within the Admiralty, which became known as Room 40. Between the wars this went on to become the Government Code and Cipher School, which at the outbreak of WW2 moved to Bletchley Park in Buckinghamshire. Here a young generation of mathematicians and scientists was recruited and they together with the veterans of Room 40 set out to break the German Enigma codes. It was here that one brilliant man, Alan Turing, saw the need for and designed a machine to help and to speed up the decoding process. Churchill continued throughout the war to provide strong support to the BP team providing both staff and finance to meet their urgent requirements.
During WW2 8,900 people were based at Bletchley Park, many of them working to decode messages that the German forces transmitted, most notably by Hitler to the German high command. The high-level intelligence produced at BP, codenamed Ultra, was crucial to the Allied war effort. The cracking of the German codes and the use of the intelligence gained, together with the subsequent related actions of the Allies was a vital part of the Allied war effort and is said to have shortened World War II by as much as two years, with the related saving of many million lives. The critical importance of Bletchley Park in world history is therefore undeniable.
Bletchley Park is also the birthplace of the world's first programmable, digital, electronic computer - Colossus. Colossus as an idea came from the operational needs of Bletchley Park during World War II to speed the reading of Enigma-encrypted German messages. Colossus Mk 1 was designed and built by a team led by engineer Tommy Flowers at the Post Office Research Station at Dollis Hill North London and went into service at BP in early 1944. by the end of the war there were ten Colossus machines in operation at Bletchley Park.
The Enigma cipher was the backbone of German military intelligence communications. The Enigma machine dated back to 1919, when Hugo Alexander Koch, a Dutchman, patented an invention that he called a secret writing machine. It was originally designed to provide secure banking communications, but the banks showed little interest. However, in 1926 the German military, initially the Navy, saw its potential and adopted it in quite large numbers, thinking it unbreakable.
However, they had not reckoned on the ingenuity of the Poles, who by 1932 had broken Enigma, when the encoding machine was undergoing trials with the German Army, and managed to reconstruct a machine. At that time, the cipher altered only once every few months. With the advent of war, it changed to at least once a day, thereby preventing Polish intercepts. By mid-1939, the Poles had passed on their knowledge to the British and the French, thus enabling the British code breakers based at Bletchley Park to work out the order in which the keys were attached to the electrical circuits, a task that had been impossible without an Enigma machine in front of them.
Fig 2. Bletchley Park mansion today
The early attempts to break the Enigma settings and coding used an equipment called the Bombe, the initial design of which was produced in 1939 at Bletchley Park by Alan Turing. The bombe was an electro-mechanical device that simulated the Enigma by trying all possible scrambler settings,its function being to discover the daily settings of the Enigma machines on the various German military nets: in particular, the set of rotors in use and their positions in the machine and the settings of the alphabet rings.
The code breakers, armed with this knowledge, were then able to exploit a loophole in Enigma's armour. One particular design flaw meant that no letter could ever be encrypted as itself: the letter A in the original message, for example, could never appear as an A in the code. This gave the code breakers a toehold. Errors in messages sent by stressed, lazy or tired German operators also provided clues. In January 1940 came the first break into Enigma.
These messages, in the form of radio signals, were initially intercepted by the network of monitoring stations (Y-Stations), which were British signals intelligence collection sites, originally established towards the end of WW1 and revived during World War II, and the traffic was then sent onwards either by motor cycle despatch rider or land line (teleprinter) to BP for de-coding and analysis. The Y-Stations were operated by a number of agencies, including the Armed services and also the Foreign Office (MI5 and MI6). Typically more than three thousand coded messages arrived at BP each day from the 'Y' Stations. Incoming messages were then routed to specific 'Huts' for decoding, depending on whether the messages had come from the German army, navy or air force, or another source. Despite the large and imposing BP manor house building, these wooden huts - Huts 3,6,4 and 8 - were where much of the Enigma decrypt work was carried out.
The huts operated in pairs and, for security reasons, were known only by their numbers. Hut 6 contained the code breakers concentrating on the German Army and Air Force ciphers, supported by a team in the neighbouring Hut 3 who turned the deciphered messages into intelligence reports. Hut 8 decoded messages from the German Navy, with Hut 4 the associated naval intelligence hut. Their raw material coming from the 'Y' Stations: the web of wireless intercept stations scattered around Britain and in a number of countries overseas. A radio station known as Station X was also sited at BP, in the mansion’s water tower, but due to the long aerials was moved to nearby Waddon Hall in 1940.
Of those working at BP more than half were women including many WRNS. Of the men, probably the most well known were mathematicians Alan Turing and Gordon Welchman. Dilly Knox, a classics scholar, was one of the original Room 40 SIGINT cell in WW1 and moved to BP in 1940 as one of the great early code breakers.
Radio was at the heart of the work of BP, because the code breakers relied on the Y station intercepts of German encrypted radio messages on which to work. Whilst Brian’s talk concentrated on the code breaking operation, there was also a huge radio network associated with the Park that carried the resulting Intelligence material to our forces round the world - including the first point-to point microwave radio relay (The No.10 set) to Montgomery after D-day - on which Dr Oakley worked as a Royal Signaller.
Dr Oakley says of these days "As a young Army signaller in 1945 I worked with many of those who had spent the war years intercepting the enemy's communications, and sending the resulting information on to Bletchley Park, where that remarkable bunch of geniuses stripped out the encoding to read the enemy's mail, something that of course gentlemen do not do! Almost in passing they launched the computer age, building what were some of the very first digital machines".
Thus the story of places such as Beaumanor Hall in Leicestershire, Denmark Hill in North London, RAF Chicksands in Bedfordshire and some thirty other widespread stations comprising 'Y' service, the Royal Signals Regiment, and the code breakers of Bletchley Park are all inter-twined.
This was a most fascinating insight into the workings of Bletchley Park and we are indebted to Brian Oakley for setting out the importance of its massive contribution in the outcome of World War 2.
John Longhurst G3VLH
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