Philip 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. Concurrently it was envisioned that phonetically 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 nomenclatures in Navajo. Initially there were twenty-nine Navajo code talkers recruited. After learning the code, twenty-five went into action and four stayed behind to teach the numerous up and coming Navajo volunteers the code. As the war progressed the baseline codes nouns, verbs, and descriptive nomenclatures were added on and incorporated program wide, and in other instances informal short cut code words were devised for a particular campaign and not disseminated 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 in turn would train the other code talkers who could not attend the meeting.
For classroom purposes, a codebook was developed to teach the many relevant words and concepts to new initiates and was never to be taken into the field. The code talker was supposed to memorize 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 quite incomprehensible because the nouns and verbs were not used in the contextual sequence of conveying meaning within a Navajo sentence structure. What the uninitiated would hear are truncated, unrelated and disjointed strings of individual unrelated nouns and verbs. The codetalkers memorized all these variations, and practiced their rapid use under stressful conditions.
Native American languages were chosen for several reasons. Most importantly, speakers of these languages were only found inside the United States – the languages were virtually unknown elsewhere. Hitler did know about the successful use of code talkers during World War I, and sent a team of some thirty anthropologists to learn Native American languages before the outbreak of World War II. However, it proved too difficult to learn all the many 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. Also the U.S. Department of War issued a memorandum to not create separate Native American units, but to integrate Native Americans in standard U.S. Army units in accordance 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. They made no sense to him, and 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 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.”
Anecdotally, Native American languages were used informally for military communications in both the European Theater of Operations (ETO) and Pacific Theater of Operations (PTO). In these instances, two-man communications teams composed of members of the same tribe were formed on an ad hoc basis by a figure of authority to address immediate tactical needs. They primarily used their native languages in unencoded conversational exchanges to transmitted military communications. These teams were not officially documented, but their stories reside in the oral histories of Native American veterans of World War I, World War II, Korea and Vietnam.
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 quite 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 (see Shibboleth). 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.