The Lamanites will be approaching from the south. Moroni divides his army, with one placed on the west side of the Sidon, and another part on the east side. We must assume that there was some easy fording place of the river. We will see that the Lamanites attempt a crossing, so there must have been a logical location for that crossing. There must also be some way of visually concealing the army on the south side of the hill Riplah, as that is the direction of approach of the Lamanite army. The tactic will be to allow the army to pass the hill, and then be caught on two fronts.