A white American man who lived with the Navajo recommended that the language be used as a code language during World War II. Back then, there were no Navajo dictionaries and very few non-Navajo spoke the language. Also, the Navajo language is very different from German and Japanese, the languages of the enemies at the time. The military started to recruit Navajo men to become code talkers. These code talkers sent code messages in Navajo. The code talkers used very specific words for military words (such as "iron fish" for submarine) so that even other Navajo would have a hard time understanding if they didn't learn the meanings of those terms. The Japanese found out they were speaking Navajo because a professor who studied Native American languages recognized it, but they could not understand the words of the code. There were other code talkers in other Native American and non-Native American languages, but the Navajo Code Talkers were the most famous.