Whether this was a decision of the generals, the Senate, or was forced on them by the wishes of the troops, who included many Carthaginian citizens, is not clear. Xanthippus, accompanied by the triumvirate of Carthaginian generals, led the army of 100 elephants, 4,000 cavalry and 12,000 infantry—the latter included the 5,000 veterans from Sicily and many citizen-militia—out of Carthage and set up camp close to the Romans in an area of open plain. The precise site is not known, but it is assumed to be close to Tunis. The Roman army of about 15,000 infantry and 500 cavalry advanced to meet them, and set up camp about away. The next morning both sides deployed for battle. Xanthippus placed the Carthaginian citizen-militia in the centre of his formation; with the Sicilian veterans and the freshly hired infantry divided on either side of them; and with the cavalry equally divided on either side of these. The elephants were deployed in a single line in front of the centre of the infantry. The Romans placed their legionary infantry in their centre, arranged in a deeper and denser formation than usual. Polybius considered this to be an effective anti-elephant formation, but points out that it shortened the frontage of the Roman infantry and made them susceptible to being out-flanked. Light infantry skirmishers were positioned in front of the legions, and the 500 cavalry were divided between the flanks. Regulus apparently hoped to punch through the elephants with his massed infantry, overcome the Carthaginian phalanx in their centre and so win the battle before he needed to worry about being attacked on the flanks. The battle opened with attacks by the Carthaginian cavalry and elephants. The Roman cavalry, hopelessly outnumbered, were soon swept away. The Roman legionaries advanced, shouting and banging their sword hilts on their shields in an attempt to deter the elephants. Part of the Roman left overlapped the line of elephants, and they charged the infantry of the Carthaginian right, who broke and fled back to their camp, pursued by the Romans. This part of the Roman force probably consisted of Latin allies (). The rest of the Roman infantry had difficulties with the elephants, who were not deterred by their noise but charged home, inflicting casualties and considerable confusion. At least some of the legionaries fought their way through the line of elephants, and attacked the Carthaginian phalanx. But they