In 1942, a group of Navajo soldiers was recruited by the US military to thwart Japanese intelligence. They were dubbed the Navajo Code Talkers. They devised a cryptographic innovation based on the Navajo language that baffled the Japenses and was indecipherable even to other Navajos.
Thanks Peg for all the great bits of information you bring. I love the code talkers story and remember it from my dad's old war stories.