Source: The Code Book by Simon Singh, 4th Estate, 1999.
Chosen: I love the story behind this statistic. At the time encrypting and decrypting messages was a time consuming business, often requiring bulky machinery. This made it difficult to accomplish in battlefield condition. A guy called Philip Johnston persuaded the U.S. military that the Navajo language was known by so few people, was so unrelated to any other language and so fiendishly difficult to learn that it could safely be used as a from of encryption. Thereafter Navajo were recruited and trained to communicate messages over the open airwaves.
Submitted by James