The initial major breakthrough happened when Alan Turing, a twenty six year old mathematician from King’s college Cambridge, developed the idea that a machine could carry out calculations when it was fed information on a strand of paper. By January 1940, Alan Turing become certain that the Polish information passed on was not entirely correct. He travelled to France to meet the Poles and asked them about their analysis of the Enigma instruction book and workings. Turing attained that he was correct in his theory and came back to England with the correct information. Straight away he started working on the messages and he completed one.
A second breakthrough was made in February 1940, by John Herivel, who was a mathematician from Cambridge University. He used the ‘crossword puzzle’ method of figuring out what the wheel settings were likely to be each day. Bletchley Park believed that the Germans thought Enigma was unbreakable and so Herivel supposed they would not be too careful when they sent the first messages, which were to establish contact with other operators. What were needed were the first messages of the day from as many operators as possible. And if they were similar they would give the settings away for that day.
During the 1940’s Alan Turing made further progress by constructing the first ‘bombes’. They were electric machines which tried to speed up the process of deciphering messages by going through all the possible combination of settings of an Enigma machine. So altogether a bombe was equivalent to ten enigma machines. A code breaker would pass on a clue which would then be run through the bombe until a message occurred. This would then be typed into a replica enigma machine to see if it resulted in a German message.
The main reason for the cracking of ‘Dolphin’ the German naval code was sheer luck and hard work. The luck being of capturing two U-boats which contained parts of an enigma machine and some instruction books. More codebooks were found on several weather ships which contained the codes to be used in June and July. From these books code breakers were then able to crack the Enigma codes for August.
The German navy then decided to change the enigma machine so it then contained four wheels which dramatically increased the number of possible settings. The new code named ‘shark’ caused two years of work to be useless. And so pressure was being put on to crack the new code. The reason that it was eventually cracked was because of the capture of two U-boats in the Mediterranean which contained code books. But more fortunately was that of the Germans still using the old Enigma, this meant that the old methods could still be used and so Bletchley Park was able to crack the codes. However that meant that there were only another twenty six variations to cracking the four wheeled version.
The last challenge that Bletchley Park faced was that of the code ‘fish’ Hitler’s personal code. To figure out the code, code breakers used the methods that they had used on enigma two years before. They looked for mistakes and repeat phrases, the Germans thought this code was unbreakable and so they were even more careless. The code breakers noticed that there was a sequence of forty one symbols, which suggested the first wheel had forty one teeth. This enabled them after two months to construct one of the machines. To make deciphering fish easier one of the code breakers designed ‘Robinson’ a machine that used two paper tapes which were run through the machine at high speeds. On one tape the German code and on the other was a key which looked for evidence of the wheel settings. However the paper tapes tended to rip and so ‘Colossus’ was invented, it was the first programmable computer and it did the same job as Robinson just with out paper tapes and at a quicker speed. This saved the code breakers time and made solving the codes easier.
The main reasons for Bletchley Park cracking the enigma code was that of German carelessness and hard work. I believe that the most important reason was that of determination and drive of the code breakers at Bletchley Park who didn’t give in even when it looked as though there was no hope.
