of Massalian ships located the Punic fleet as it lay at anchor, and slipped away undetected to warn Gnaeus of the Carthaginian presence. The Roman fleet sailed from Tarraco and was positioned only 10 miles to the north of the Carthaginian position when the warnings reached Gnaeus Scipio. Gnaeus manned his ships with picked legionaries, and now sailed down to attack the Punic fleet. Hasdrubal's army scouts detected the approaching Roman fleet before the Punic navy and warned their fleet of the coming danger through fire signals. Most of the crews had been foraging, and they hastily had to man their ships and sail out in a disorderly manner. There was little coordination and some ships were undermanned because of the surprise achieved by the Romans. As Himilco sailed out, Hasdrubal drew up his army on the shore to give encouragement to his fleet. The combat effectiveness of the Carthaginians is not reflected in the number of ships as one-quarter of their fleet had newly trained crew. The Romans formed 2 lines with the Roman ships in front and the Massalian ships behind them, with the formation and the naval skill of the Massalians nullifying the superior manoeuvrability of the Carthaginian fleet. The Romans engaged the Carthaginian ships as they came out of the river, ramming and sinking four of them and boarding and capturing two more. The Carthaginian crews then lost heart, beached their ships and sought safety among the army. The Romans grappled and hauled away 23 of the beached ships. Aftermath and importance The defeat proved to be decisive in the long run. Hasdrubal was obliged to march back to Cartagena, fearing seaborne attacks on Carthaginian territories. With the Iberian contingent of the Carthaginian navy shattered, Hasdrubal was forced to either call Carthage for reinforcements or build new ships. He did neither. The performance of the Iberian crews had been poor in the battle, and their dismissal would spark a rebellion in the Turdetani tribe, forcing Carthage to send 4,000 infantry and 500 cavalry to Hasdrubal. Hasdrubal would spend all of 216 BC subduing the rebels. In 217 BC, the main Carthaginian fleet captured a supply fleet headed for Iberia off Cosa in Italy. Publius Cornelius Scipio arrived in Iberia with 8,000 soldiers in the fall of that year with instructions from the Roman Senate to prevent any help from reaching Hannibal in Italy from Iberia. This