The Ammonite Defenders were the Nephite armies tasked with the protection of the converted Lamanites, known as the people of Ammon or Anti-Nephi-Lehies, after they settled in the land of Jershon. Following their conversion to the gospel and subsequent rejection of any form of violence, the people of Ammon feared taking up arms against their brethren, the Lamanites, because of their past sins and profound repentance. In response to this situation, the Nephite people offered them the land of Jershon as an inheritance, accompanied by a promise of protection (Alma 27:22-24).
The Nephite forces established a defensive position between the land of Jershon and the land of Nephi, creating a buffer to protect the Ammonites from Lamanite aggression. The defense agreement included a reciprocation clause wherein the Ammonites would support the Nephite armies with a portion of their substance, thereby ensuring the armies could be maintained. This arrangement allowed the Ammonites to live in peace, fulfilling their covenant to abstain from warfare, while the Nephites, in an act of brotherly support, safeguarded their land and lives.