rotor settings for any given message, and the code clerk changed those settings with every message he sent.

The path the electrical current took initiated with the keystroke. The current passed through the plugboard, changing its path if that letter was plugged to a different letter. From there it entered the first, or rightmost, rotor at the input contact. The rotor wiring redirected it to a different output that went directly into the next rotor's input. After passing through, and changing directions in each rotor, the current entered a reflecting plate. This plate not only changed the 'letter,' but also sent the current back through the rotors, again resulting in three more changes. The current made one last pass through the stecker and finally on to the light panel where the cipher letter lit up.

To decipher an Enigma message, the recipient had to have an Enigma with the same plugboard connections, rotors, notch placement, left/center/right positions, and initial settings. This enabled the current to follow the same pathway in reverse and resulted in the plaintext letter lighting up on the light panel. The Germans, with their published key lists, had the necessary information. The Allies did not. The Enigma eliminated whatever intricacies a language may possess that previous methods of cryptanalysis exploited. One such practice was frequency counts. Certain letters in any language are used more often than others. By counting which cipher letters appeared most often, cryptanalysts could make an assumption about which plaintext letter they represented. Machine encryption like the Enigma destroyed the frequency counts. Cipher letters tended to appear equally often.

Poland Breaks the Unbreakable Machine

In 1928 the Poles, who had actively intercepted German signals since the end of the First World War, realized that the Germans had changed to machine encryption because standard attacks, such