Ammon’s sword is the weapon Ammon used against men who lifted clubs to smite him. He “smote off their arms with his sword” and with “the edge of his sword,” causing them to flee before him (Alma 17:37). He slew none with the sword except their leader (Alma 17:38).
After Ammon had driven them afar off, they watered their flocks and returned them to the pasture of the king. They went in unto the king bearing arms “smitten off by the sword of Ammon” from those who sought to slay him (Alma 17:39).
Ammon later “raised his sword” and said, “I will smite thee except thou wilt grant unto me that my brethren may be cast out of prison” (Alma 20:22).