According to an article by John Tvedtnes, typically Mesoamerican peoples had six basic classes or occupations: peasants, merchants, warriors, priests, judges, and government officials. Among the Aztecs, all of these were directly involved in war. For example, the merchants formed, when necessary, their own military units. Warriors and priests replenished the ranks of the judges and other government officials and most priests began their service for a time in special military units. Aztec boys destined for a military career were dedicated for the task at birth by their parents and trained at an early age. This fact of Mesoamerican life is reflected in the youth of the Nephite chief captains. It would explain how a 25 year old Moroni and later a sixteen year old Mormon came to command the Nephite armies at what we would consider in our culture to be an extremely young age.
Also of significance was the fact that the Aztec war lord, though elected to his position, was generally a blood relative of the Chief Speaker (king). Among the Maya, the town governor (batab) was a hereditary office with judicial and military functions, much like those exercised by the earlier Moroni in the Book of Mormon. There was also a war captain (nacom) who was elected for three years, but during all-out war, the batab was expected to lead the army. Though not identical to the Nephite military organization, there are obvious similarities. [John A. Tvedtnes, "Book of Mormon Tribal Affiliation and Military Castes," in Warfare in the Book of Mormon, F.A.R.M.S., p. 318]
Moroni Was Only Twenty and Five Years Old when He Was Appointed Chief Captain
According to Cleon Skousen, we should pause for a moment to mention that Alma 43:17 raises an important question. Mormon tells us that Moroni was only 25 when he was appointed chief captain. But when was that? Many scholars have used this present verse as the basis for assuming that Moroni was only 25 in 74 B.C., when the war with Zerahemna broke out. However, subsequent events would clearly suggest that this is not realistic. For example, just 14 years later (in 60 B.C.) Moroni turned over the military leadership to a son who was old enough and sufficiently seasoned to become chief captain (Alma 62:43). Four years after that, Moroni died (Alma 63:3). Now if Moroni were only 25 (74 B.C.) he would have retired at 39 and died at 43. Obviously, this does not appear reasonable, and we must therefore conclude that Moroni had been appointed chief captain several years before this war with Zerahemnah in 74 B.C. In fact, when we trace back the military history of this period, we find that the last identified commander prior to Moroni was a man named Zoram. He had charge of the Nephite armies as of 81 B.C. (Alma 16:5). There was another war in 77 B.C. when the Lamanites came down against the people of Ammon (Alma, chapter 28), but the name of the chief captain is not given. It is believed that sometime between 81 B.C. and 77 B.C., Moroni became the chief captain of the Nephites.
If we assume Moroni became chief captain in 81 B.C. (shortly after the war in which Zoram was commander), then Moroni would have been 32 in 74 B.C. when the war with Zerahemna broke out. Fourteen years later when he resigned he would have been 46--which would have allowed time for his son Moronihah to mature and replace him. This would mean that when he died four years later he would have reached the age of fifty. Considering all the circumstances, this seems to be a relative approximation of the chronology of Moroni's life. [W. Cleon Skousen, Treasures from the Book of Mormon, Vol. 3, p. 3087]
Note* Could the change in military leadership from Zoram to Moroni have any thing to do with the rebellion of the Zoramites? [Alan C. Miner, Personal Notes] [See Appendix A]