Once it was dark, Hannibal sent the various components of his army on night marches behind the hills to the north of the lake to take up positions from which they could ambush the Roman army. Night marches are notoriously difficult and often result in units becoming lost in the dark or alerting their enemy. The Carthaginians avoided both of these and took up positions on the reverse slopes of the hills. The Carthaginian cavalry were positioned furthest to the west, the north Italian Gallic infantry to their east and the experienced African and Iberian infantry furthest east, relatively close to their camp. Modern historians place the bulk of the large number of Carthaginian light infantry either around the defile and its mouth or as reinforcing the Gauls in the centre of the Carthaginian line.