He sailed at once for Carthage, and began by rescuing one of the generals who were about to be superseded from a dangerous position into which his imprudence had led him. Then he set the affairs of the army in order. The camp was cleared of a crowd of idlers, soldiers' servants, sutlers, and dealers. Then active operations were begun. A suburb of the city, called Megara, where the wealthier citizens had their homes, was taken. It was soon relinquished, indeed, for it was found too costly to keep, but this success led to the abandonment of the camp which had been fortified outside the walls, and which was the first line of defence. The city was now almost invested. On the land side the blockade was complete, and no more supplies could be introduced; and now Scipio began to block up the mouth of the harbour. But here the besieged foiled him. They built a fleet of fifty ships, and they dug a new channel from the inner harbour to the open sea. The Romans were taken by surprise. They had no idea that a fleet was being built, and they saw it for the first time when it issued from a harbour which was also a new creation. If the Carthaginians had acted at once, for they found the Roman fleet wholly unprepared for action, they might at least postponed the end. But they contented themselves with a demonstration. A day or two after there was a drawn battle between the two fleets, but when the conflict was renewed on the morrow, the advantage rested with Rome. But the resources of the besieged were not exhausted. An attack was made on the city on the land-side, and battering-rams were brought up to the walls. But the besieged made a determined sally, drove back the assailants, and burnt their engines. During the winter Scipio busied himself with cutting off the supplies that the city still received from the interior. He also routed an army of native allies which had been gathered for its relief.