ABSTRACT
But what if the Allies had not been able to crack enemy communications? e question cannot be answered with a single response. e Axis utilized many different communications systems. e Japanese, for instance, depended not only on its chief naval code, but also an administrative code, a flag officers’ code, an army transport code, air codes, and many low-level military tactical codes, to mention only some. e Germans likewise used not only their famed Enigma cipher machine but also the tactical double-square cipher, whose key
changed every twelve hours, two different on-line teletypewriter cipher machines, the naval dockyard cipher, a plenitude of constantly changing ground-to-air systems, and some local cryptosystems. Even the Enigma was used in a variety of ways. Each service gave each of its communications nets its own key for the Enigma. Every corps in the army, for example, had one. e Kriegsmarine in particular divided its Enigma settings keys between U-boats and surface vessels and between various coastal commands. Solution of messages in one key did not automatically give the Allies access to messages in other keys. And some Enigma messages, like those used by the Luftwaffe, were relatively easily and almost constantly solved, while others, like those used by the U-boats, sometimes were solved and sometimes were not.
