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Station X was the codename given to Bletchley Park, a stately home that became the base for the allied code breakers during the Second World War. Purchased in 1939, the buyer claimed it was being turned into an air defence training school. Of the people who were recruited to work there, they were told that they were to tell nobody the nature of their work, except their wives, where absolutely necessary.

The Germans had been using Enigma machines to encode all their secret military information that they wished to send to outposts. The code was considered unbreakable, and as such had been largely ignored since World War One. In 1939 there were originally four code breakers trying to crack the Enigma code, led by the eccentric but brilliant Dilly Knox. The problem these men had was that by varying the settings within the machine and wiring up a play board to the front of it, the Germans were able to choose from 159,000,000,000,000 settings. As long as both machines involved in message reception and message sending were set up the same, the receiver would receive a message in fluent German.

Due to the difficulty that the original code breakers were having, the first set of mathematicians to be involved in the code breaking process were drafted in to Station X. The theory that was used in trying to crack a cipher was to try and find features that corresponded to the original plain text. One way would be to look for letter frequency, so in English E would be one of the most frequent letters. From this, contact analysis could be performed, so if one letter were found to be T followed by a middle letter then an E the middle letter could be assumed to be an H. The Enigma machine guarded against these methods by moving the wheels of the machine after twenty-six strokes, so hardly any letter frequency could be built up. The code breakers were helped by the Germans in their orderly way of doing things though. Very often messages encoded on the Enigma machines would start with the same announcement, for example ‘To the Group’. Codes could often be broken using these phrases, which were known as cribs.

Alan Turing, a brilliant mathematician, was the first man to crack Enigma. Anybody who knew was sworn to secrecy. If the Germans knew the code breakers of Station X had been successful, they would refine their machines.

Different types of Enigma code were assigned a colour, and when John Herivel managed to break into Red Enigma the intercepts suggested Hitler was about to invade Britain, leading Churchill to give some of his finest ‘bulldog spirit’ speeches. The attack by sea never came but air raids were a constant threat. For much of the time though, the code breakers were able to forecast where the strikes would take place. This was helped in no small part by the development of a machine by Alan Turing called a bombe. With the help of cribs these would statistically test each possibility, making the code breaking process quicker.

The work of Station X was often hampered by a breakdown in communication, often due to a lack of trust on behalf of people at the Admiralties Operational Intelligence centre, for example. They considered Station X to be civilians and this is where the distrust came from. It was to lead directly to the deaths of more than 1500 men aboard HMS Glorious (Aircraft carrier) and HMS Acasta and Ardent (battleships). The trust began to grow however, and interception of Enigma by Station X led to the sinking of the Bismarck in May 1941.

The code breakers also cracked Dolphin Enigma, which was used by the U boats, thus protecting the merchant ships bringing supplies from North America in the first battle of the Atlantic.

At the start of the war 200 people had been drafted into Station X, but by December 1942 this number had risen to 3500, many of whom were Navy Wrens operating the bombes. The now regular cracking of Enigma had put a new slant on the war with Special Signals links being set up on the front line of battle where commanders could get immediate Enigma information sent to them. This was particularly true of the battle of North Africa.

Rommel, The Desert Fox, had eventually managed to take Tobruk, mainly down to the poor tactics of Sir Claude Auchinleck, an English officer. He was replaced by General Montgomery, who guessed Rommel’s next move and had them confirmed by the code breakers at Station X. This gave Montgomery a huge advantage and after weeks of battle Rommel retreated from Africa never to return.

Another example of the code breakers influence on the war came when the U boats resumed attacks on the Atlantic convoys in August 1942. They had refined their Enigma machines, making the codes more difficult to break. Station X broke the codes just in time with the country nearing the point of starvation.

Later in the war code breakers from America were invited to Station X, and after a brief period of distrust on both sides, they were able to help make the invasion of Europe a success.