Culture: This verse introduces basic information on the organization of the Nephite army. A. Brent Merrill, a former major in the U.S. Air Force, describes the basic system:
The Book of Mormon suggests that the Nephite military structure was based on the decimal system, similar to that in use in the vicinity of ancient Palestine and in many other regions. There are references to units of fifty (see Mosiah 11:19), thousands (see Alma 43:5, 60:22; 3 Ne. 3:22), and ten thousand (see Morm. 6:10–15). The only Israelite-sized units not specifically mentioned in Nephite-Lamanite organizations are formations of tens and hundreds. Possibly these too existed among Book of Mormon people but were not mentioned because of their relative unimportance and because they comprised part of other units, like fifties and thousands.
The numbers used in the Book of Mormon may or may not represent actual counts. (See Helaman, Part 1: Context, Chapter 4, “The Meaning of Numbers: Counts and Estimates in the Book of Mormon.”)
Merrill further notes:
Perhaps the best single description of Nephite military organization during the reign of the judges is found in Alma 2:13. This verse states that the Nephites “appointed captains, and higher captains, and chief captains, according to their numbers”—meaning according to the number of men each type of captain commanded. This all sounds very similar to the statements reported earlier by Ixtlilxochitl and other sixteenth-century writers about Mesoamerican captains. These accounts speak of “captains,” “five minor leaders or captains,” and “great” captains or “chiefs.”
Confirming how many men each captain, higher captain, or chief captain supervised is impossible with the data currently available. It is tempting to say each chief captain commanded a unit of ten thousand, but the Book of Mormon text does not always support this assertion. Some chief captains commanded all the armies of the Nephites while others almost certainly commanded units smaller than ten thousand (see Alma 52;19, 27–28; 55:23; 56:12; 57:29). It seems impossible that every chief captain mentioned in these verses had ten thousand troops under his command. Battle conditions and casualty reports do not support such a conclusion.
Most likely the term “chief captain” was part of a title for commanders with units of one thousand or more: “chief captain of a thousand,” “chief captain of ten thousand, or “chief captain of the armies of the Nephites.” If these assumptions are correct, the “higher captains” possibly commanded formations of one hundred or more men, and “captains” as used in Alma 2:13) might have commanded units of fifty or fewer.