The Code talkers were Native American soldiers serving in the U.S. armed forces who primarily transmitted secret tactical messages. The Code Talkers transmitted these messages over military telephone or radio communications nets using formal or informally developed codes built upon their native languages.

The name is strongly associated with bilingual Navajo language speakers specially recruited, for the first time during World War II, by the United States Marine Corps, under the Dept. of the Navy to serve in their standard communications units in the Pacific Theater. However the United States Army, under the Dept. of War, also used Native American Indians to perform the same missions in both World War I and World War II.

Use of Navajo language

Phillip Johnston proposed the use of the Navajo language to the United States Marine Corps. The idea was accepted and the Navajo code was formally developed and centered on the Joint Army/Navy Phonetic Alphabet that uses agreed upon English letters to spell out words. For each English letter in the phonetic alphabet system the code talkers were asked to generate several nouns and sometimes verbs in the Navajo language using the principle of letter and word substitution. It was envisioned that spelling out all military terms letter by letter into words in combat can be time consuming, so some terms, concepts, tactics and instruments of modern warfare were given uniquely formal descriptive names in Navajo.

As the war progressed the baseline codes nouns, verbs, and descriptive names were added on and incorporated program wide, and informal short cut code words were devised for a particular campaign and not spread beyond the area of operation. To ensure that a consistent use of code terminologies were used Pacific Theater wide, representative code talkers of each of the U.S. Marine divisions met in Hawaii to discuss shortcomings in the code and incorporated new terms into the system and update their codebooks. These representatives would train the other code talkers who could not attend the meeting.

For classroom purposes, a codebook was developed to teach many relevant words and concepts to new initiates and was never to be taken into the field. The code talker was supposed to retain all the English/Navajo and Navajo/English word associations in the codebook. To an ordinary Navajo speaker, the entire code talking 'conversation' would have been difficult to comprehend since the nouns and verbs were not used in the contextual sequence of conveying terms in a Navajo sentence structure. What the uninitiated would hear are truncated, unrelated and disjointed strings of individual unrelated nouns and verbs. Here is a link to see the now-declassified "Navajo Code Talkers' Dictionary." The codetalkers memorized and practiced these variations  rapidly under stressful conditions.

Cryptographic properties

Native American languages were chosen for several reasons. Most importantly, speakers of these languages were only found in the United States - the languages were virtually unknown at other locations. Hitler did know about the usage of code talkers during World War I, and sent a team of thirty anthropologists to learn Native American languages before the outbreak of World War II. However, it proved too difficult to learn all the languages and dialects that existed. Because of Nazi German anthropologists' attempts to learn the languages,  the U.S. Army did not implement a code talker program in the European Theater. The U.S. Department of War also issued a memorandum not to create separate, but to integrate Native Americans in standard U.S. Army units with standard recruitment procedures.

The Navajo spoken code is not very complex by cryptographic standards, and would likely have been broken if a native speaker and trained cryptographers worked together effectively. The Japanese had an opportunity to attempt this when they captured Joe Kieyoomia in the Philippines in 1942. Kieyoomia, a Navajo Sergeant in the U.S. Army, was ordered to interpret the radio messages later in the war. However, as Kieyoomia had not participated in the code training, the messages made no sense to him. When he reported that he could not understand the messages, his captors tortured him. Given the simplicity of the alphabet code involved, it is probable that the code could have been broken easily if Kieyoomia's knowledge of the language had been exploited more effectively by Japanese cryptographers.

The Imperial Japanese Army and Navy never cracked the spoken code, and high ranking military officers have stated that the United States would never have won the Battle of Iwo Jima without the secrecy afforded by the code talkers. The code talkers received no recognition until the declassification of the operation in 1968. In 1982, the code talkers were given a Certificate of Recognition by President Reagan, who also named August 14 "National Code Talkers Day."

Six Navajo Code Talkers pause for a group photo on the first day of location shooting for the "back to the battlefields" segment of the documentary that will chronicle their lives and times. Pictured at a Memorial on Guam honoring native Chamarro "scouts" for the Marine Corps during World War II, from left to right, are Samuel Sandoval, Teddy Draper, Sr., Samuel Tso, Albert Smith, Samuel ("Jesse") Smith, and Keith Little. (Photo by Katy Gross)

An unfamiliar spoken human language is harder to crack than a code based on a familiar language. The languages chosen had little written literature, so even researching them was difficult for non-speakers. Also, many grammatical structures in these languages are different from any the enemies would be expected to know, adding another layer of incomprehensibility. Non-speakers would find it extremely difficult to accurately distinguish unfamiliar sounds used in these languages. Additionally, a speaker who used the language all his life sounds distinctly different from a person who learned it in adulthood, thus reducing the chance of successful imposters sending false messages. Finally, the additional layer of an alphabet cypher was added to prevent interception by native speakers not trained as code talkers, in the event of their capture by the Japanese. A similar system employing the Welsh language was used by British forces, but not to any great extent.

Comanche and Hopi code talkers

There were 17 Comanche tribesmen who were recruited by the 4th Infantry division before World War II and who also developed a formal code system centered around the Joint Army/Navy Phonetic Alphabet. This local divisional initiative was never expanded and these 14 remained with the unit until the end of World War II. The division participated in D-Day, the Battle of Normandy. The last Comanche "code talker" from World War II, Charles Chibitty, died in 2005. Their code name for Adolf Hitler and German units associated with him was "Crazy white man." Under a similar local unit initiative, a small group of Hopis were also recruited into an Artillery Battalion to develop a formal code system, also centered around the Joint Army/Navy Phonetic Alphabet, and participated in the Philippines campaign.

Source

Aaseng, Nathan. "Navajo Code Talkers: America’s Secret Weapon in World War II." New York: Walker & Company (1992).

Durrett, Deanne. "Unsung Heroes of World War II: The Story of the Navajo Code Talkers." Library of American Indian History, Facts on File, Inc. (1998).

McClain, Salley. "Navajo Weapon: The Navajo Code Talkers". Tucson, Arizona: Rio Nuevo Publishers (2001).

Meadows, William C. "The Comanche Code Talkers of World War II". Austin: University of Texas Press (2002).

David Kahn. "The Codebreakers - The Story of Secret Writing." (1967).