When Chester Nez passed away June 4 at the age of 93, it marked the end of an era. Nez was the last living member of the first group of Navajo code talkers, a group of Native Americans recruited into the United States Marine Corps as a secret weapon to help win World War II.

The code talkers were not weapons or combat soldiers in the conventional sense. Instead, they were brought into the military for something singular only they possessed: their native tongue. The Navajo language became the central component of a new cryptographic code that proved unbreakable for decades.

The use of code talkers actually dates back to World War I, when 14 Choctaw soldiers helped American forces win several battles against the German army in France. The U.S. military again turned to Native Americans in WWII, employing several Comanche men to create secret messages in the European theater, 27 Meskwaki men in North Africa, and Basque speakers in Hawaii and Australia. But it was the Navajo code talkers, who worked primarily in the Pacific, who had the greatest impact.

According to the official Naval History & Heritage website, the idea for using the Navajo language originated with a civil engineer named Philip Johnston, who had grown up on the Navajo reservation with his missionary father. At the time, Navajo remained an unwritten language. It also possessed extremely complex syntax and no alphabet, making it "unintelligible to anyone without extensive exposure and training." In tests, Johnston proved that the code was not only unbreakable, Navajo soldiers could encode a message in just 20 seconds. Cryptographic machinery of the day required 30 minutes to complete the same task.

The first 29 Navajo code talker recruits arrived in May 1942. They quickly created a dictionary and code words for common military terms ("submarine" became "iron fish"). The entire system, as described on the Naval history site, was incredibly complex:

When a Navajo code talker received a message, what he heard was a string of seemingly unrelated Navajo words. The code talker first had to translate each Navajo word into its English equivalent. Then he used only the first letter of the English equivalent in spelling an English word. Thus, the Navajo words "wol-la-chee" (ant), "be-la-sana" (apple) and "tse-nill" (axe) all stood for the letter "a." One way to say the word "Navy" in Navajo code would be "tsah (needle) wol-la-chee (ant) ah-keh-di- glini (victor) tsah-ah-dzoh (yucca)."

Nez told CNN in 2011 that they "were careful to use every day Navajo words" in their code "so that we could memorize and retain the words easily." They were expected to memorize the code, which Nez said "helped us to be successful in the heat of battle."

Each code talker was deployed to the Pacific with a unit of Marines. There, they transmitted messages and orders about tactics, troop movements and other orders. The Japanese heard these messages but were never able to decode them. Numerous battles, in particle the Battle of Iwo Jima, were won due to this strategic advantage.

The irony of this was not lost on Nez. As he recounted in his 2011 book, "Code Talker: The First and Only Memoir by One of the Original Navajo Code Talkers," he was not allowed to speak the Navajo language growing up in the 1920s, when the government-run boarding school that he attended tried to beat his culture out of him. But the experience — as well as the Navajo culture, which the government could not erase — toughened him. In the book, he describes a battle on Guam that left him with a piece of shrapnel in his left foot. "I said nothing, just gritted my teeth," he wrote. "We Navajo men never screamed when we were hit, and we waited for someone else to call the medic. We'd been raised to suffer silently."

About 400 additional Navajo joined Nez and the other original 28 code talkers. Their existence and their role in the military remained a secret until it was declassified in 1968. The code talkers all received the Congressional Gold Medal in 2001.

In a statement released soon after Nez's death, the Marine Corps praised his legacy. "We mourn his passing but honor and celebrate the indomitable spirit and dedication of those Marines who became known as the Navajo Code Talkers. The incredible bravery, dedicated service and sacrifices of Mr. Nez and his fellow Code Talkers will forever remain part of the proud legacy of our Corps and will continue to inspire generations of Marines into the future."

The official Navajo Code Talkers website contains numerous articles about and interviews with the veterans, including this interview Nez recorded in 2012:

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