On Wednesday Chester Nez, one of the 29 original Navajo code talkers who worked for the US during WWII sending secret messages in their native language, died in his home in Albuquerque, New Mexico. Nez was 93, and his death was confirmed by Judy Avila, who helped him write his memoirs, according to The Los Angeles Times.

Nez was one of the first code talkers recruited for the job in 1942, while the US was seeing its codes broken over and over again by Japanese code breakers. According to AZCentral, he was in tenth grade when he was recruited by US Marines, who came to his boarding school in Arizona looking for native Navajo speakers.

Navajo has a complex grammar, and at the time there were few, if any, written records of the language. CNN notes that Nez and his peers were forbidden to speak Navajo growing up—until, of course, they were needed to devise a code based on the language. The 29 Navajo men attended boot camp at Camp Pendelton in California and there devised a dictionary with special words for military terms that did not exist in Navajo. They then memorized that dictionary, as the Naval History and Heritage Command recounts:

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)." Most letters had more than one Navajo word representing them. Not all words had to be spelled out letter by letter. The developers of the original code assigned Navajo words to represent about 450 frequently used military terms that did not exist in the Navajo language. Several examples: "besh- lo" (iron fish) meant "submarine," "dah-he- tih-hi" (hummingbird) meant "fighter plane" and "debeh-li-zine" (black street) meant "squad."

The Navajo code talkers were primarily employed in the Pacific Theater of Operations, and Nez himself served in the thick of fighting in Guadalcanal, Guam, Peleliu, and Bougainville.

“In developing our code, we were careful to use everyday Navajo words, so that we could memorize and retain the words easily,” Nez told CNN in 2011. “I think that made our job easier, and I think it helped us to be successful in the heat of battle. Still, I worried every day that I might make an error that cost American lives. But our code was the only code in modern warfare that was never broken. The Japanese tried, but they couldn’t decipher it. Not even another Navajo could decipher it if he wasn’t a code talker.”

The US Marines eventually recruited more Navajo speakers, and by 1945 somewhere between 375 to 420 were working as code talkers. The code talkers were forbidden from discussing their work until 1968, when the program was declassified.

Breakthroughs made during WWII in cryptography were hugely important for computing and information security in the following years and decades. And the Navajo code talkers have their own part in that history. As Robert Graham of Errata Security tweeted tonight, "WW II Navajo Code Talkers: proof that 'security through obscurity' works."