A bit more info and background
Lacking secure battlefield voice communications during the Great War, the Army employed Choctaws to encrypt voice communications, using their native language, itself encoded.
The Army studied the program even before war was declared in 1941, and during World War II employed Commanches, Choctaws, Kiowas, Winnebagos, Seminoles, Navajos, Hopis and Cherokees. The Marine Corps took the Army work and codified, expanded, refined and perfected it into a true security discipline, using Navajos exclusively. In campaigns against the enemy on many fronts, the Native American Codetalkers never made a mistake in transmission nor were their codes ever broken.
I have spoken with several of the code talkers who live in the Taos area.
Some of them are pretty colorful characters.