Courtesy of Pacific Paratrooper
During WWI, the Choctaw language had been used to transmit U.S. military messages. With this thought in mind, Philip Johnston, the son of a missionary grew up on a Navajo reservation and spoke the Diné tongue fluently, brought the suggestion of a similar code to General Clayton Vogel early in 1942. The Diné language has no alphabet, uses no symbols and one sound may hold an entire concept. The idea was tested and proved to be faster and more reliable than the mechanized methods. The language has more verbs than nouns, that helps to move the sentences along and makes it far more difficult for outsiders to learn – making it the most ingenious and successful code in military history.
Much more at his site – (name is live link)