Secret Services & Bombe 2.0

"The Poles had proved that Enigma was not a perfect cipher, and they had also demonstrated to the Allies the value of employing mathematicians as codebreakers." 

The room 40, which was shortely substituted by the GC&CS settled in Bletchley Park, 80 kilometers (50 miles) north of London, started to recrute new operator especially between mathematicians and scientists, and one of them, who deserves to be singled
out, it is the mathematician Alan Turing, who identified Enigma’s greatest weakness and ruthlessly exploited it. Thanks to Turing, it became possible to crack the Enigma cipher under even the most difficult circumstances.

The basic idea was that many messages sent would consist of some short piece of predictable text such as "The weather today will be...."  for the morning weather report, or "Heil Hitler" as closure of each text. Using those cribs the cryptoanalyst were able to create a menu  like the one in the photo below

The menu, in the form of an electric circuit, was ‘plugged up’ on the panel of sockets located on the back of the Bombe by means of 26-way cables. It must be underlined that, for the correct functioning of the British Bomb,  it was essential that the structure of the menu included multiple ‘closures’ or loops.

In the given menu the sequence of letters: S → A → X → V form one such loop, and the diagram below gives the details of the Enigma enciphering processes that correspond to the four links in this loop. In this diagram the four unknown stecker partners of the letters S, A, X and V are respectively represented by the Greek letters: α, β, γ and δ. (The Enigma rotor systems and their equivalents on the Bombe will subsequently be referred to as the ‘scramblers’. The scrambler connections were made with 26-way cables.)

The American Bombe was in its structure similar to its british correspondent, although it was way faster because it was designed to find the key of a 4 (instead of only 3) rotors Enigma, which was the one employed by the Kriegsmarine, the German Naval Army, the safest one.

The capability of the Allies to read the Axis messages allowed them to win importants battles of the Second World War, like for the Battle of the Atlantic, and the war itself.

The Entire argument of Cracking the Enigma Machine started in the last post Secret Services & Cracking Enigma: The Bombe,

Sources:
The Code Book, Simon Singh
http://www.rutherfordjournal.org/article030108.html
http://www.bletchleypark.org.uk/content/machines.rhtm
http://www.vectorsite.net/ttcode_08.html#m1
http://en.wikipedia.org/wiki/Bombe
http://ciphermachines.com/enigma.html#break