Welchman helped improve Alan Turing's design of the Polish electromechanical Enigma-cipher-breaking machine, the bombe. Welchman's 'diagonal board', made the device much more efficient in the attack on the ciphers of the German Enigma machine. Bombes became the main mechanical aid in breaking Enigma ciphers during the war. They speeded up the search for current wheel order settings being used with the Enigma machines. The settings were changed often, initially at least once per day.