The Navajo Code Talkers were one of America’s secret weapons in World War II. They helped the United States Marines ( 海军陆战队 ) send oral communications that the enemy could not translate. Usually the enemy could understand even messages sent in secret code ( 密码 ). However, the Navajo Code was never broken. It remained a secret even at the end of the war. The tradition of Native Americans helping with communication during wartime began in World War I. Soldiers from Choctaw and Comanche tribes ( 部落 ) successfully used their own languages to send secret messages for the Americans. In World War II, the same technique was used again. This time the soldiers came from many tribes. The contribution of the Navajo was unique, however. The Navajo have a particularly difficult language that few people outside the tribe could speak at the time. In 1942, 29 Navajo marines were asked to create a code based on their native language. This made the code even tougher to break. Also, this code was never to be written down. It was to be memorized. When the U.S. Marines began work on the Navajo Code, they chose and memorized 26 words to stand for the letters of the English alphabet ( 字母表 ). Then they added a vocabulary list of 211 words, which later grew to 411 words as other Navajos joined the code team. They carefully designed a code that did not contain patterns. If the enemy could recognize patterns, they could eventually break the code and understand the messages. The Navajos memorized their work, taught it to new participants, and practiced using it in many situations. Then they put their knowledge to work on the battlefields. These men were the senders and receivers of the messages—the Code Talkers. About 420 Navajo marines served as Code Talkers in the South Pacific during World War II. Their excellent memories made them very swift and accurate in translating the messages written in the Navajo Code. They deciphered them almost instantly, while a code machine could take as long as four hours. It was the only oral code never broken during the war. The Code Talkers were amazingly cool under fire. For instance, Iwo Jima was a bloody, 36-day battle. However, even in the midst of the battle, the Code Talkers translated their messages calmly and clearly. Iwo Jima was the turning point of the fight in the South Pacific, and the Code Talkers played a vital part in winning it. The government kept the Code Talkers as secret as possible. Even at the end of the war in 1945, their work remained a secret. The U.S. government feared that the Navajo Code might have to be used again. Not until 1969 did the government finally tell the public about the achievements of these men during World War II. Even today, not many Americans realize what a valuable contribution the Navajo Code Talkers made to winning the war.