> all knew that the Enigma had been cracked, but Admiral Doenitz refused to believe it.
Whereas:
The dropping results made Admiral Dönitz suspicious. Although reassured by the Abwehr, the German Foreign Intelligence, that Enigma was unbreakable, he insisted on improving the security of Enigma. On 1 February 1942 the famous Enigma M4 model with four rotors and new key sheets were introduced.
There were multiple Enigma variations, based on rotor choice pool sizes, number of fittable rotors, time cycles to changing procedures, etc. Some naval enigma variations were broken, others weren't.
Whereas:
~ https://www.ciphermachinesandcryptology.com/en/enigmauboats....~ https://uboat.net/technical/enigma_ciphers.htm
There were multiple Enigma variations, based on rotor choice pool sizes, number of fittable rotors, time cycles to changing procedures, etc. Some naval enigma variations were broken, others weren't.