What was everyone else doing?
Of course, the Germans weren’t the only player in 20th-century geopolitics to encrypt their messages. The British took Enigma, added some extra bits to it, and produced Typex, a sevenrotor machine that the German Beobachtungsdienst (Observation Service) of Naval Intelligence never broke into despite reading most other British radio traffic during the war.
Beobachtungsdienst was based in Berlin, however, and Allied bombing raids destroyed many of its records. This, along with the British taking up the practice of superencipherment (enciphering a message using one method, then again using another) meant that by 1944, no British ciphers in use could be read.
In the United States, the Japanese diplomatic cipher known as Purple was of more interest, and the intelligence it provided was code-named Magic. Purple was again a modified Enigma, but used stepping switches instead of rotors, and was known in Japan as the System 97 Typewriter for European Characters. The US Army Signal Intelligence Service reverse-engineered the system and had a machine that could read Purple by late 1940, but would not obtain the fragmentary remains of a genuine machine until 1945. As the Japanese ambassador in Berlin tended to brief his government in great detail using Purple (reviews of German assessments of the military situation, reports on direct inspections by the ambassador, including Normandy beach defenses, reviews of strategy and intentions, and reports of interviews with Hitler), Magic was of great interest to the British, and two of the reverse-engineered Purple machines ended up in British hands.
The Japanese naval cipher, JN-25, was trickier. Tiltman and Turing at Bletchley Park worked out quite early that it enciphered words as five-digit numbers using a codebook, then used a second codebook as superencipherment. Without the codebooks, however, they couldn’t read it, and in 1940 the Japanese Navy wasn’t sending many messages. But after Pearl Harbor, there was more traffic, and the Japanese habit of starting messages with “I have the honor to inform your excellency...” led to it being broken.