History – Bletchley Park
Located 50 miles from London, Bletchley Park played an unsung role in the history of World War II. It was from here that many of the brightest young men and women on the Allied side worked to break the German military codes. Their work enabled the Allies to decipher significant volumes of German military traffic, allowing for the successful execution of the D-Day landings, and it is estimated that their work shortened the course of the war by up to two years.

In their work, these codebreakers were utilising the latest developments in technology – the work of such men as Alan Turing, leading many to call Bletchley Park the ‘home of modern computing’.

In 1938, with the threat of war imminent, the Government Code and Cipher School, then based in London, needed a safer home where its intelligence work could carry on unhindered by enemy air attacks. At a junction of major road, rail and teleprinter connections to all parts of the country, Bletchley Park was chosen as the optimum location.

Commanded by Alastair Denniston, the Park was given the cover name Station X, being the tenth of a large number of sites acquired by MI6 for its wartime operations. The role of the Government Code and Cipher school was to break enemy codes, in this instance the primary threat was the Enigma cipher machine.

The German military used the Enigma cipher machine during WW2 to keep their communications secret. The machine was available commercially during the 1920s, but the military potential of the device was quickly realised and the German army, navy and air force all used a more developed model of the machine to encipher their messages believing that it would make these communications impenetrable to the enemy.

The German authorities believed in the absolute security of the Enigma. However, with the help of Polish mathematicians who had managed to acquire a machine prior to the outbreak of WW2, British code breakers stationed at Bletchley Park managed to exploit weaknesses in the machine and how it was used and were able to crack the Enigma code.

Before the war started, the Poles passed all of their information over to the Britain and France and two mathematicians working at Bletchley Park, Alan Turing and Gordon Welchman, were able to build on this research to develop the ‘Bombe’ machine. Turing and Welchman exploited the fact that enciphered German messages often contained common words or phrases, such as general’s names or weather reports and so were able to guess short parts of the original message. These guesses were called ‘cribs’. The fact that on an Enigma machine no letter can be enciphered as itself made guessing a small part of the text even easier. It also meant that the potential number of settings that the Enigma could be in on that day was greatly reduced. A rebuilt Bombe machine can be found at Bletchley Park.