sentences:  The pro-Roman Volcae, acting on behalf of a Roman army camped on the east bank near Massalia, intended to prevent the Carthaginians from crossing and invading Italy.Devising a plan to circumvent the Volcae, the Carthaginians, before crossing the river to attack the Gauls, had sent a detachment upriver under Hanno, son of Bomilcar, to cross at a different point and take position behind the Gauls.Hannibal led the main army across after Hanno sent smoke signals saying that the ambush was in place.