Every Code Talker carried the entire system in his memory: every military term and its Navajo equivalent, every letter of the substitution alphabet and its multiple Navajo representations, every nuance of pronunciation that distinguished one code word from another.

By the time the first Code Talkers were deployed, the original vocabulary had been expanded, refined, and committed to the memories of a growing group of trained communicators.

The program that began with twenty-nine men would ultimately involve somewhere in the range of 375 to 420 Navajo men over the course of the war — the National Archives provides this range as an estimate, and historians note that the precise count is complicated by record-keeping questions and the classified nature of the program during and after the war.

Claiming a single precise number misrepresents what the records actually support.

Guadalcanal: The First Test in Battle

The first operational deployment of Navajo Code Talkers came during the Guadalcanal campaign, which began in August 1942.