The speed advantage was real.

And the security — the fact that Japanese signals intelligence was unable to make anything of what it intercepted — was genuine.

The Code Grows Larger

As the program expanded through 1943 and into 1944, the vocabulary of the code grew along with it.

The original approximately 200 terms were expanded to more than 400, then beyond, as the scope of Pacific operations grew and the need to communicate increasingly diverse tactical and operational information became apparent.

New terms were developed for specific weapons systems that had come into operational use since the code was first designed.