“August 14 is National Navajo Code Talkers Day, a day to commemorate the contributions of Native American code talkers who served in the U.S. military during World Wars I and II. Code talkers utilized a secret, coded language, based on their native language, to communicate important information over military telephones and radios.”
https://nationalvmm.org/national-navajo-code-talkers-day/
Learn more:
https://americanindian.si.edu/visit/washington/nnavm
https://blogs.loc.gov/law/2020/08/navajo-code-talkers-day/