According to the Book of Mormon, Ammon was a prominent Nephite missionary, and son of King Mosiah. He was originally opposed to the church but, along with his brothers and Alma the Younger, was miraculously converted. Following his conversion he served a mission to the Lamanites and converted Lamoni and his people.
Early Life and Conversion
As one of the four sons of King Mosiah, Ammon had tremendous influence among his people, the Nephites. He rejected the Church and attempted to turn the people from the teachings of the prophets. Because of the fervent prayers of their parents, Alma the Younger and the four sons of Mosiah had a conversion experience much like that of Saul of Tarsus. An angel appeared to them on the road and rebuked them for their wickedness. The shock put Alma the Younger into an insensible state for a time; the specific effect upon Ammon is not recorded, but he became fully converted to the Gospel and desired to serve as a missionary to the Lamanites.
Ammon and his brothers spent several years teaching the Gospel to the Lamanites. Ammon chose to go first to the land of Ishmael. He was captured by the Lamanites and taken before their king, Lamoni. Lamoni asked his purpose in straying so far from Nephite lands. When Ammon replied that he wanted only to serve, the king, impressed, offered him one of the king's daughters. Ammon refused but became a servant in the king's household, assisting others in caring for his sheep.
When bandits attacked their flocks one day, the other servants fled but Ammon stood his ground and was miraculously protected. Ammon was granted supernatural strength and actually cut off the arms of each robber who attacked him. His great power convinced the servants, and the king, that he was favored of God. The king, his household, and the entire kingdom were converted to the Gospel.
Later, Lamoni's love and respect for Ammon impressed Lamoni's father, the king of all the Lamanites. As a result, the Lamanite king accepted the teachings of Aaron, Ammon's brother, and was baptized. The Lamanites converted as a result of Ammon's ministry were called the "Anti-Nephi-Lehies" until they changed their name to the People of Ammon after their migration to the Nephite land of Jershon. They swore never to take up arms again, and never did, although the Two thousand stripling warriors were recruited from among their sons.