According to Shirley Heater, the Printer's Manuscript of the Book of Mormon differs somewhat from the Original Manuscript. . . . At present in the 1981 LDS edition, Alma 43:17 reads, "And Moroni took all the command, and the government of their wars. And he was only twenty and five years old when he was appointed chief captain over the armies of the Nephites." The Original Manuscript says that "he was appointed chief commander over the armies of the Nephites." Apparently this word on the Original Manuscript was copied incorrectly on the Printer's Manuscript and carried forward. [Shirley R. Heater, "Variances Between the Original and Printer's Manuscripts," in Recent Book of Mormon Developments, Vol. 2, pp. 80, 87]
Note* The reader should be aware, however, that there are multiple other references to the position of "chief captain" over the Nephite armies (for example: Alma 2:13; 16:5; 43:16). [Alan C. Miner, Personal Notes]
Alma 43:17 [Moroni] was appointed chief captain over the armies of the Nephites ([Illustration]): Moroni Instructs Generals [Gary Kapp, Verse Markers, Book of Mormon, Vol. 1, p. 2]