Code talkers were Navajo Indians who provided secure communications for the U.S. military’s Pacific operations during World War II (1939–45). Serving in the marines, the Navajo servicemen were recruited because of their language, which is unwritten and extremely complex. Military officials believed the Japanese would not be able to decipher intercepted communiqués that were transmitted in the Navajo language. The first Navajo recruits attended boot camp in May 1942 and developed and memorized a dictionary of military terms to use in encrypting messages. The trained code talkers were deployed with marine units throughout the Pacific theater. They worked around the clock, with tremendous speed and accuracy, to transmit vital information about military tactics, battle orders, and troop movements. Their messages were sent over telephone and radio; because of the complexity of the language, the Japanese military was never able to break the code. About 400 Navajos served as code talkers during the war, contributing mightily to the success of U.S. military assaults at Guadalcanal, Iwo Jima, and other Pacific venues.