Rotor from Enigma cypher machine, 1939-1945.
© Science Museum / Science & Society Picture Library
This view of the rotor shows the wiring between the contact studs and the spring loaded contacts. Throughout World War II, Germany and its allies encrypted military communiques using Enigma machines and, by 1945, over 40,000 such machines were in use. The Germans considered the Enigma code to be unbreakable, but the codebreakers at Bletchley Park in Buckinghamshire, the British forces' intelligence centre, managed to decipher the code with the help of 'Bombe' codebreaking machines.