nationals from both countries working alongside each other. Often devices developed in the UK were wholly manufactured in the USA; for many weapons and machines this became Britain’s arsenal, with American productive technology manufacturing most of the ships, tanks, aircraft, and armaments that eventually overwhelmed the Axis powers (see Chapter 6).
The fact that Anglo-American technologists had virtually a free hand to develop novel equipment, coupled with the immense productive capacity of the USA, meant that Anglo-American leaders were blessed with equipment vastly superior to that of their enemies.
After a mere 21 years of uneasy peace, the world was at war again – a war in which technology would play a crucial role in securing victory for Britain and her allies. Meanwhile in a mansion in Buckinghamshire, many brains were already hard at work trying to decipher the enemy’s messages…
BLETCHLEY PARK TIMELINE
The Enigma Encrypting Machine
1920s German engineer Arthur Scherbius invents the Enigma electro-mechanical encrypting machine. Used commercially and also by several governments, including Germany, to protect military and diplomatic communications.
1932 Polish mathematician and cryptologist Marian Rejewski partly breaks the German encryption system. French spy working in Germany acquires further information which the French passed to the Poles who are then able to read German messages and build their own replica machines.
1938 Germans develop a more complex machine which the Poles are unable to read.
1939 In July the Poles inform French and British cryptologists of their work and, after the outbreak of war, they and their equipment are evacuated to France. They also give one of their replica machines to British cryptologists.
1940 Following the fall of France, the Poles move first to Vichy, France, and then to Britain in November 1942, where they collaborate with British cryptologists.
British Decrypting Work
1938 Government Code and Cypher School (GC&CS) acquires Bletchley Park, Buckinghamshire.
1939 Recruitment of academics, mathematicians etc. by GC&CS. Separate huts established to tackle the different systems used by each of the German armed forces.
1940 HMS Griffin captures German trawler. Some naval codes temporarily broken.
1941 The Germans start using the more sophisticated Lorenz cypher machines. The British name deciphered Lorenz messages Tunny.
Alan Turing and Gordon Welchman develop a Bombe to speed up decoding procedures.
In May, a RN ship obtains Enigma machine and code books from a sinking U-boat.
In December Germany declares war on USA and American cryptologists start working with their British counterparts at Bletchley Park.
1942–43 Post Office engineer Thomas Flowers builds Colossus which implements Turing/Welchman proposals and enables Lorenz signals to be read more speedily.
1945 Government orders destruction of all machines.
A BATTLE OF WITS
Bletchley and beyond
In 1938 the British Government Code and Cypher School (GC&CS) acquired Bletchley Park, Buckinghamshire (in present-day Milton Keynes) as its headquarters. On the outbreak of war it recruited a number of top-level academics – particularly mathematicians and linguists, but also historians, chess champions, and crossword addicts – to work on decrypting German radio intelligence signals picked up by intercept stations (see Y-service). The German signals were encoded using the highly sophisticated Enigma and Lorenz encrypting machines, amongst others, which produced coded messages that the Germans regarded as unbreakable.
Thanks to incredibly brilliant decrypting work by the Bletchley Park cryptologists, coupled with the development of electro-mechanical computing machines, the Enigma (and later, even more sophisticated systems) was broken. As a result, the Allied High Command was informed of German plans and dispositions, often within a few hours of their radio transmission.
Many women worked at Bletchley Park, some as cryptologists but several more providing various support services. In particular there were many hundreds of Wrens (WRNS – Women’s Royal Naval Service) who assisted in the operation of the decrypting machines. A few Wren officers also served as decrypting officers in the troopships converted from the fast peacetime passenger liners whose speed enabled them to cross the oceans unescorted. If Bletchley Park decrypts suggested U-boats might be approaching, signals were sent instructing them to change course.
Down Memory Lane
At the end of the war the decoding machines and many relevant papers were destroyed. (The machines now on display at the museum in Bletchley Park are recently constructed replicas.) Due to the loyalty of those who worked there during the war, all of whom were bound by the Official Secrets Act, the whole Bletchley Park operation remained unknown to the public until the 1970s and 1980s when there started to be leaks about its activities; following this some of those involved wrote their memoirs. Lately its operations have been described in a number of books and portrayed in films and television programmes. Bletchley Park’s present-day successor is the Government Communications Headquarters (GCHQ) at Cheltenham.
The decoded information, called Ultra, had a profound effect on the outcome of the Battles of the Atlantic and Alamein, and the North Africa and north-west Europe campaigns. It has been claimed that the knowledge gained through Ultra shortened the war by two years. After the entry of the USA into the war American cryptanalysts worked alongside their British counterparts at Bletchley Park. ‘It was thanks to Ultra,’ Churchill is credited with saying, ‘that we won the war.’
Enigma
Originally invented by a German engineer around 1920, early Enigma encoding machines were used commercially but were later adopted by the German military who also upgraded them. The Poles were also working on them; by December 1932 they had broken the German cyphers. They also built replica machines and, five weeks before the outbreak of the Second World War, they gave replica equipment to the British GC&CS and their French equivalent together with details of their decryption techniques.
Courtesy of Greg Goebel
The Enigma machines worked on electro-mechanical principles and had five rotors, each with a variety of settings which were generally changed on a daily basis, meaning time was always of the essence – it was calculated that there could have been 159x1018 possible daily keys.
Separate coding systems were used by each of the German services, adding to the difficulties of their decryption. As the numbers working at Bletchley Park increased, wooden huts were built in the grounds, with each hut’s occupants dealing with separate aspects of the decrypting operation. Hut 6 under Gordon Welchman was responsible for dealing with Army and Air Force codes, while Navy codes were the responsibility of Hut 8, which was initially controlled by
