Alma 43:17

and Moroni took all the command, and the governments of their wars.—And he was only twenty and five years old when he was appointed Chief Commander over the armies of the Nephites.

Moroni led all the armies and directed all their wars. He was only twenty-five years old when he became the chief commander of the Nephite armies.

Moroni took command of all their military forces and strategy. He was only twenty-five years old when he was appointed chief commander.