The Galatians - John D. Grainger

The eastern Celtic tribes, known to the Greeks as Galatians, exploited the waning of Macedonian power after Alexander the Great's death to launch increasingly ambitious raids and expeditions into the Balkans. In 279 BC they launched a major invasion, defeating and beheading the Macedonian king, Ptolemy Keraunos, before sacking the Greeks' most sacred oracle at Delphi. Eventually forced to withdraw northwards, they were defeated by Antigonus Gonatus at Lysimachia in 277 BC but remained a threat.
A large Galatian contingent was invited to cross to Asia to intervene in a war in Bithynia but they went on to seize much of central Anatolia for themselves, founding the state of Galatia. Antiochos I curbed their power in 'the Elephant Victory in 273 BC' but they remained a force in the region and their fierce warriors served as mercenaries in many armies throughout the eastern Mediterranean. John Grainger narrates and analyses the fortunes of these eastern Celts down to their eventual subjugation by the Romans, Galatia becoming a Roman province in 30 BC.