Cumeni is the next logical military target because it is the next Lamanite-held city. The approach here is a complete siege, cutting it off from all reinforcements and supplies. When the Nephite spies saw a supply train approaching, Helaman’s troops surprised Cumeni’s inhabitants by cutting off that city with a night maneuver.
While night maneuvers are very difficult, this one is made easier because the Nephite soldiers can break out of battle formation as they wait. This luxury is thanks to the reinforcements from Zarahemla; since before they arrived, Helaman probably lacked sufficient men to surround Cumeni.
The timing shows that Helaman understood the problems of besieging a city. While defensible, the cities nevertheless required food to function. Cumeni is now, after Antiparah’s fall, on the front line, so the Lamanites cannot safely till its fields. They must be supplied from other Lamanite-held cities. When a new supply train comes, it signals that those who are waiting for it are probably nearing the end of their stores and therefore require replenishment. Cutting off this resupply train leaves Cumeni with the fewest possible provisions. Again this strategy presages techniques documented for the later Aztecs. Hassig notes: “The mere existence of fortifications was not always a guarantee of safety in war. One of the Aztecs’ main considerations in battle and in siege operations was to prevent outside help from reaching the defenders.”