According to Brant Gardner, the attempt to slay Ammon by the father of Lamoni, who was the over-king (see Alma 20:20) appears to be an oddity. This event should not happen in the canons of Western thought. First of all it is unthinkable for a king to travel without an army to do his fighting for him. We do not know whether or not such an army was with Lamoni's father, but they certainly do not enter into this conflict. Secondly we have a man clearly old enough to have an enthroned son, and he seems to have no hesitation in attempting to wage hand-to-hand combat with a strong youthful Ammon who quickly has the king begging for his life. What is going on?
It is in the Mesoamerican canons of conflict that we find our most reasonable context for this event. In Mesoamerica, great emphasis was placed on the personal performance of the ruler in warfare, an emphasis sufficiently great that there are records of relatively aged kings presenting their captives. In a system which expects military prowess of its kings, and which exalts the captives of the kings in stone as did the Classic Maya cities, this personal confrontation has a comfortable home. [Brant Gardner, "A Social History of the Early Nephites," delivered at the FAIR Conference, August 17, 2001, p. 11]
Gardner notes that an extreme example of an aged king engaged in warfare is found in the story of Itzamnaj B'alam II of Yaxchilan who is listed as taking a war captive when he was in his eighties. The authors do suggest that he was only the figurehead and that the actual fighting might have been done by his vassals, but that is a supposition just as his individual participation is a supposition. [Brant Gardner, Book of Mormon Commentary, [http://www.highfiber.com/~nahualli/LDStopics/Alma/Alma20.htm], p. 7]