 The Marine Corps began recruiting Navajo code-talkers, which were Navajo Native Americans who used obscure languages as a means of secret communication during wartime between 1941 and 1942. The Marines' primary job was to use their knowledge of Native American languages as a basis to transmit coded technical messages. Philip Johnston was a World War I veteran who had heard about the successes of the Choctaw Telephone Squad, which was a group of Choctaw Native Americans who pioneered the use of Native American language as military code. Johnston, although not Native American, had grown up on a Navajo reservation. In 1942, he suggested to the Marine Corps that the Navajos and other tribes could be very helpful in maintaining secret communications. After viewing a demonstration of messages sent in the Navajo language, the Marine Corps was so impressed that they recruited 29 Navajos in two weeks to develop a code within their language. Old words had to be short and easily learned and recalled. The men developed a two-part code. A 26-letter phonetic alphabet used Navajo names for 18 animals or birds, plus the words ice, the letter i, nut, n, quiver, q, ute, u, victor, v, cross, x, yuka, y, and zinc for z. The second part was a 211-word English vocabulary with Navajo synonyms. Conventional Marine Corps codes involved lengthy encoding and deciphering procedures using sophisticated electronic equipment. The Navajo code, relying on the senders and the receiver's brains, mouths, and ears, was much faster. In training and in combat, code talkers' proficiency erased general distrust. After the Navajo code was developed, the Marine Corps established a code talking school. The school progressed, more than 400 Navajos were eventually recruited as code talkers. The training was intense. Following their basic training, the code talkers completed extensive training in communications and memorizing the code. This secret, unbreakable code language that was used to send information on tactics, troop movements, and orders over the radio and telephone was indecipherable to the enemy and a key factor in the American military victories at Iwo Jima, Saipan, and several other major battles in the Pacific Theater. The deployment of the Navajo code talkers continued through the Korean War and was ended early in the Vietnam War. The Navajo code is the only spoken military code never to have been deciphered.