Unlike the Germans' infamous Engima code, one of the most successful codes used during World War II was not produced by a machine. Instead, it was developed and implemented by Navajo Indians serving in the U.S. Marines. Based on the ancient language of the Navajo, the code was unbreakable because so few people in the world then knew or understood the language. The contributions of the servicemen, now referred to as the "Navajo Code Talkers," were vital in keeping the enemy unaware of the activities and plans of American forces during the war.