A colonel was a silver eagle.

A captain was a two-star.

The entire table of organization and equipment of a Marine division could be communicated through this system of substitutions without using a single English word.

The second level was an alphabet.

For spelling out proper names — of places, of individuals, of units — that did not have assigned code words, the Code Talkers used a substitution alphabet in which each letter of the English alphabet was represented by a Navajo word beginning with the corresponding sound.

The letter A, for example, could be transmitted as the Navajo word for ant, apple, or ax — three different options for the same letter, a feature that prevented frequency analysis from identifying the most commonly used letters by the frequency of the words representing them.