Cryptanalysis of the Enigma
![The Enigma machine was used commercially from the early 1920s and was adopted by the militaries and governments of various countries—most famously, Nazi Germany.](/Images/godic/202501/04/EnigmaMachineLabeled5636.jpg")
![A series of three rotors from an Enigma machine scrambler. When loaded in the machine, these rotors connect with the entry plate on the right and the reflector drum on the left.](/Images/godic/202501/04/Enigma_rotor_set5636.png")
![The plugboard (Steckerbrett) was positioned at the front of the machine, below the keys. In the above photograph, two pairs of letters have been swapped (A↔J and S↔O). During World War II, ten leads were used, leaving only six letters 'unsteckered'.](/Images/godic/202501/04/Enigma-plugboard5636.jpg")
![Marian Rejewski about 1932, when he first broke Enigma](/Images/godic/202501/04/MR_1932_small5636.jpg")
Cryptanalysis of the Enigma enabled the western Allies in World War II to read substantial amounts of secret Morse-coded radio communications of the Axis powers that had been enciphered using Enigma machines. This yielded military intelligence which, along with that from other decrypted Axis radio and teleprinter transmissions, was given the codename Ultra. This was considered by western Supreme Allied Commander Dwight D. Eisenhower to have been "decisive" to the Allied victory.