What was Enigma machine used for?
Intelligence gathered by decrypting Enigma was known as ‘Ultra’. Much work was done at Station X, Bletchley Park, by Alan Turing & others. The achilles heel of the Enigma machine, whether it was 3 rotor or 4 (Used by the Kreigsmarine) was that it would not type the same letter as the letter to be encrypted. The name of the computer that eventually cracked Enigma was Colossus. Quite how it was all done is way beyond my field of expertese !