The U.S. first used Native American code talkers in the First World War. Most were Choctaw Indians who used their tribal language to transmit orders and other communications on telephone lines.
In 1940, the army began recruiting Comanches, Choctaws, Hopis, Cherokees, Mohawks and others for its communications program.
The U.S. Marine Corps began its own program in 1941, primarily recruiting Navajo from the American Southwest. Eventually, more than 400 Navaho code talkers would serve with the marines.
The Germans and Japanese had begun studying Native American languages between the wars to foil the code talkers, but Navajo proved to be an especially difficult language for non-Navajo to learn. Tests by the marines showed the code talkers to be faster and easier to use than encryption machines.
The Navajo developed two types of messages. In Type One Codes, a Navajo word was chosen to represent each letter in the English alphabet and the code talker would spell out the message in Navaho words.
Type Two Code translated the entire message into Navajo, frequently using invented words that didn’t exist in Navajo to convey technical military terms or jargon.
The last Navajo code talker, Chester Nez, died in 2014.
Canada recruited code talkers, too.
Charles “Checker” Tompkins, a Métis from Saskatchewan, was one of several fluent Cree speakers who served Canada in the Second World War. Tompkins was assigned to the U.S. Eighth Air Force to transmit radio messages in Cree. His story is told in a short 2016 documentary, Cree Code Talker, by Indigenous filmmakers Alexandra Lazarowich and Cowboy Smithx.
The Canadian code talking program was declassified in 1963 and the U.S. Program in 1968.
Source: National Museum of the American Indian, Canadian Encyclopedia