Polybius was born at Megalopolis in Arcadia, which was one of the staunchest members of the Achaean League in its last desperate stand for freedom in the second century b.c. The Hellenistic civilization had been unable to achieve permanent unity in Hellas, and in the second century petty quarrels between neighbouring states seemed likely to overshadow the real danger from without. The dynasties of Ptolemies, Seleucids, and Antigonids were becoming divided amongst themselves; Rome was growing and inevitably meeting opposition from Carthage; Greece was liable to become the battleground, or else fall a prey to the victors. Credit for being the pioneer in the policy of arousing the dormant Achaean League to a realization of its ideals of Greek union and freedom belongs to Aratus of Sikyon: for the accomplishment of the task of uniting the Peloponnese against the danger which threatened, three men are chiefly responsible, Philopoemen who became head of the League after the death of Aratus (213 b.c.), Lycortas, and his son Polybius. All three were natives of Megalopolis, a city which was itself originally an experiment in unity.