Cryptanalysis of the Enigma Bletchley Park to describe the network that used the same Enigma setting sheets. Initially these were recorded using coloured pencils and were given the names "red", "light blue" etc., and later the names of birds such as "kestrel". During World War II the settings for most networks lasted for 24 hours, although towards the end of the war, some were changed more frequently. The sheets had columns specifying, for each day of the month, the rotors to be used and their positions, the ring positions and the plugboard connections. For security, the dates were in reverse chronological order down the
Arizona during World War II Johnston, a World War I veteran who had lived in the Navajo reservation of Arizona and was fluent in the Navajo language. Johnston and the "original twenty-nine," as they were known, are credited with developing the original code, however, it was modified and improved by others as the war progressed. At least 540 Navajos served in the Marine Corps during World War II, about 400 of whom were trained as code talkers. Because many of them lacked birth certificates, it was impossible to verify the age of some recruits. After the war it was revealed that boys as young as