Someone can correct me if I'm wrong but I was under the impression that they where the first to realize that the Enigma machine wasn't able to map any letter on

Someone can correct me if I'm wrong but I was under the impression that they where the first to realize that the Enigma machine wasn't able to map any letter onto itself. This being the core principle behind all of the machines built to crack the messages, guess part of the plaintext message and discard all the enigma settings which could not have produced that cipher text.