The Navajo language has mainly only been used on the reservation. It is a complicated unwritten language, which few outsiders were or are exposed to. In 1942, to assist in the war effort, the Navajo Code Talker Program was established.

The person who started the program was Philip Johnston. As a child, he was raised on the Navajo reservation, grew up with Navajo children and learned their language. He felt that the use of Navajo would produce an unbreakable code, with its complexity in syntax and tones, which would assist the war effort.

When recruiters went to the reservation, the response from the Navajo was enthusiastic. Johnston himself took part in the training.

The code was used to transmit secret messages, and was used with great success throughout the World War 2, especially in the Pacific Campaign. It is acknowledged that this code remained unbroken, and is probably the only unbroken code in all of war history.

By the end of the program over 400 Navajo code talkers had been enlisted by the United States Marine Corps. The entire Navajo population was about 50,000.

The idea of using a relatively unknown Native Indian language as code was not new. The U.S. had used Cherokee to transmit messages in the early part of World War 1. And towards the end of the war, Choctaw was used. During World War 2, Comanche and Meskwaki were also used. But none of these was on the scale of the Navajo program.

The Navajo code talkers were widely used. They took part in all the U.S. Marines' operations in the Pacific. Without them, many believe that the Battle of Iwo Jima would not have been won. Navajo code talkers not infrequently got mistaken as Japanese soldiers, and to avoid the danger of getting shot or killed by their own soldiers, some commanders arranged a bodyguard for each code talker.

In 1942 Joe Kieyeoomia, a Navajo Sergeant, was captured in the Philippines. The Japanese made him interpret radio messages. But he had not done any code training, and he could not understand the messages. For his failure to interpret, he was tortured.

The Japanese, who were skilled code breakers, never managed to decipher the Navajo code talkers' code.

There is an interesting story of how Hitler, aware of the previous use of code talkers in World War 1, despatched a number of anthropologists to learn Native American languages before World War 2 began.

But the number and difficulty of the languages proved too much for them. Nonetheless, because of Hitler's attempt to pre-empt the use of code talkers, the U.S. made only limited use of code-talker programs in the European theatre. In the Invasion of Normandy, fourteen Comanche code talkers were employed.

Because of its secrecy, the code talkers were given recognition and honoured only relatively recently. Their achievements were almost forgotten after the war ended. The program was declassified in 1968. In 1982, President Reagan named August 14 "Navajo Code Talkers Day".

Twenty-nine Navajo code talkers were awarded the Congressional Gold Medal in 2000. In 2001 President Bush presented the Medal to four of the five surviving code talkers.