Hugh Nibley
"But how was a major city, superbly fortified by Moroni's own foresight, to be taken? The first step was a logical one. It was the ancient custom of warfare to invite the occupants of a city to come out on the open plain and engage in a fair set contest, or, as the Nephites put it, 'upon fair grounds'; fn the Nephite commanders in issuing such an invitation to the comfortably ensconced opposition hardly expected the Lamanites to comply with a request so disadvantageous to themselves, but they thought it was worth a try and at any rate it was the conventional thing to do (Alma 52:19-20). Their next move was to try a decoy trick. Teancum allowed the Lamanites to discover a task-force of his moving along the coast and to give it chase; Moroni then slipped into the city behind them and overpowered the defenders, characteristically sparing all who yielded up their arms (Alma 52:22-25)." (Since Cumorah, p. 314)