cryptanalysts in Poland. They realized that the time-consuming hand-worked method of analysis would not be sufficient. Marian Rejewski developed plans for a machine that could, through brute force, work through the more than 17,000 possible positions.(3)The machine was called a Bomba.(4)

AVA Radio Manufacturing Company (Wytwornia Radiotechniczna AVA), the same company that built the Polish copies of the Enigma, also built the first Bomby (the plural of Bomba) for the Polish cipher bureau. It resembled three pairs of Enigma duplicates linked together. The new Bomby and Zygalski's sheets worked well, finding solutions in two hours or less through 1938. Then the Germans added two new rotors to the collection. Although the Enigma machine continued to use only three rotors at a time, the Poles had no way of knowing which three out of five had been selected. Rejewski determined the wiring of the new rotors as he had the original three, but the Bomba was not built to work through the combinations available with a choice of five rotors. Instead of having six interlinked Enigmas, the Bomba would need sixty. It was more than the Polish system could handle.

On July 25 and 26, 1939, with the threat of German invasion looming over them, the Poles shared their cryptanalytic secret with the French and British. Despite the French-Polish agreement and the contribution of German information that France provided, Poland had never disclosed the break in the Enigma messages. The French and British representatives were astonished to see not only Enigma replicas, but also a machine that could break the Enigma settings. Returning home with copies of the Enigma, each renewed efforts to break the German encryption.

Britian Builds the Bombe

Britain, like Poland, began hiring mathematicians to work in their Government Code and Cipher School (GC&CS). Alan Turing and Gordon Welchman, both mathematicians from Cambridge