Navajo made a good basis for a code for several reasons. Any unknown language is very hard to figure out if it is not related to a known one. There were very few non Navajos who spoke the language at the time. Some estimates put that number at 30-40 people. Dictionaries and grammars had not been published internationally. Although it is very similar to Apache it is not understandable to others (in Canada and Alaska) in the larger language family, the Na-Dene. It was very hard for mainly non native speakers because the consonants are difficult, the vowels can be tonal and nasalized and the grammar is complex. It the guy whose idea it was, Philip Johntson, had grown up on the Navajo reservation, the son of a missionary and spoke the language and had been in the Army in WWI. There were also a large enough group of young Navajos who were fluent in Navajo. This was not the case for many other native languages. This was because Navajo are one of the largest tribes, and it was very remote area in the 1940's so most still spoke Navajo. many young men in their 20's had learned English in boarding schools.
The man who taught a Navajo class that I took in Kayenta, AZ had been punished for speaking Navajo and not knowing English when he entered boarding school in Chinle at age 7.
The code was not just spoken Navajo so to native speakers it would sound like a strange string of words. Basically it was a alphabet substitution code. So if you wanted to spell an english word that started with c, you would have cat stand for "c" and use the navajo word for cat, "mósí". Sometimes to mix it up you could use the would cow, Navajo for cow is "béégashii"
Note: in these examples the marks over the vowels means those vowels are high tone, those without marks are low tone.
Navajo Language
I believe you are referring to the Navajo Code Talkers. The Navajos were recruited to use their language to speak in code and sent Morse code in the Navajo Code. The Japanese could not recognize the language.
There were no Navajo code "breakers" . That means someone who tries to figure out and unknown code. Native Americans who worked for the American side in World War II were sometimes called "code talkers". They used a substitution code to encode English orders using a native American language, mostly Navajo but other ones were used too.
Code Talkers were specially trained in the art of code talking in the language of the Navajo people. As I understand it, most were of Navajo descent but not all.
no one but them knew the language so it became a useful code language
The Navajo and 11 Hopi soldiers used the the easiest of the Navajo language, to help America defeat the Japanese.
Navajo Indians were used in WW2 to transmit messages in their language which was very effective as a code. It was never broken.
In the book "Code Talker" by Joseph Bruchac, a metaphor that is used is comparing the Navajo language to a code that the enemy cannot break. This metaphor emphasizes the power and significance of the Navajo language in the war effort.
The language is of the Navajos, an American Indian tribe. Axis had never seen the language, therefore it was perfect as code.
The Navajo Code Talkers were people who used a spoken code in the Navajo language to communicate between US units on the battlefield in the Pacific Theater of War during World War 2.
The military utilized Navajo men who fashioned a secret code from their ancient Navejo language to relay messages of vital importance to the war effort. Navajo language was not decipherable to enemy
The code talkers were native American from the Navajo tribe. They used their native language to send messages that the Japanese couldn't decode or understand.