Polybius seems to have returned to the Peloponnese at once, and to have remained there until B.C. 149, when he was suddenly summoned to serve the government whose enforced guest he had been so long. It was the year in which the Senate had determined to commence their proceedings against Carthage, which were not to be stayed until she was levelled with the ground. In B.C. 150 the victory of Massanissa had restored the oligarchs, who had been superseded by the popular anti-Roman party in Carthage. These men hastened to make every possible offer of submission to Rome. The Senate had made up its mind for war; and yet did not at once say so. After demanding that full satisfaction should be made to Massanissa, it next decreed that the Carthaginians must at once give three hundred of their noblest youths as hostages to the Roman consuls Manilius and Censorinus, who had sailed to Lilybaeum with secret orders to let no concession induce them to stop the war until Carthage was destroyed.[35] There was naturally some hesitation in obeying this demand at Carthage; for the hostages were to be given to the Romans absolutely without any terms, and without any security. They felt that it was practically a surrender of their city. To overcome this hesitation Manilius sent for Polybius, perhaps because he had known and respected him at Rome, and believed that he could trust him; perhaps because his well-known opinion, as to the safety in trusting the Roman _fides_, might make him a useful agent. But also probably because he was known to many influential Carthaginians, and perhaps spoke their language.[36] He started for Lilybaeum at once. But when he reached Corcyra he was met with the news that the hostages had been given up to the consul: he thought, therefore, that the chance of war was at an end, and he returned to the Peloponnese.[37] He must soon have learnt his mistake. The Consul, in accordance with his secret instructions,—first to secure the arms in Carthage, and then to insist on the destruction of the town,—gradually let the wretched people know the extent of the submission required of them. These outrageous demands resulted in the Carthaginians taking the desperate resolution of standing a siege. Censorinus and his colleague accordingly began operations; but they were not capable of so great an undertaking. The eyes of the whole army were turned upon Scipio Aemilianus, who was serving as a military tribune. The siege lingered through the summer of B.C. 148 without any result; and when in the autumn Scipio left for Rome, to stand for the Aedileship, he started amidst loud expressions of hope that he might return as Consul, though below the legal age.[38]