Japan knew it was the Navajo language. It wasn’t just the language, it was the Code that the Code Talkers had developed among themselves.

The Japanese captured a Navajo artillery soldier in the Philippines.

The Japanese tried unsuccessfully to have him decode messages in the “Navajo Code” used by the United States Marine Corps, but although Kieyoomia understood Navajo, the messages sounded like nonsense to him because even though the code was based on the Navajo language, it was decipherable only by individuals specifically trained in its usage.

Kieyoomia is notable for having not only survived the Bataan death march and related internment and torture in a concentration camp, but also being a hibakusha (survivor of an atomic bomb blast).

Diné Bizaad – The Navajo Language is an oral language. It is a difficult language and was an isolated language at the time of WWII. A written language was being worked on but was not widely circulated. 

The number of phonemes in Navajo is disputed, but many scholars agree that there are thirty-three consonants, including a large number of affricates and fricatives, and twelve vowel sounds. Length is phonemic in Navajo, and vowels appear either short, long, or overlong.

Navajo syllables carry either a high, low, rising, or falling tone. Falling and rising tone can occur on long syllables. A rising tone is marked in the orthography by the acute accent on the second vowel, while falling is marked by the acute accent on the first syllable.

The Navahos call themselves: “Dine” which means men or people and in conversing with them they will tell you that “Dine” simply means “The People”.

The Apache-Navajo language and the other Athabascan languages belong to an entirely different language family from the Amerindian languages.

One crucial difference that separates them from the other Amerindian languages and suggests their affinity to the languages of east Asia is that they are tonal; i.e., words with the same phonemes but spoken with different tones have different meanings. (emphasis added) This meant that it was almost impossible for adult outsiders to learn these languages.