 With an estimated population of 50 million in 480 BC, the Achaemenid Empire at its peak ruled over 44% of the world's population, the highest such figure for any empire in history.The Greco-Persian Wars eventually culminated with the independence of Persia's westernmost territories (comprising Macedon, Thrace, and Paeonia) and the definitive withdrawal from the Balkans and Eastern Europe proper.In 333 B.C, following the Battle of Gaugamela, the Empire was overthrown and incorporated by Alexander the Great, starting a new period in Middle Eastern history, one noted by the emergence of Hellenistic and Greco-Persian culture, as well as dynasties (e.g.