As part of an alliance with Mithradates of Pontus, they settled in lands belonging to Seleucia. War ensued, and the king of Seleucia was killed in 261 BC. They were defeated by Attalus of Pergamon in 240 BC.
Due to their proximity to the Greek-speaking world of the time, the tribal rule of these Biblical Celts has been preserved.
Each of the three tribes was divided into quarters - four 'septs' or clans. Each 'sept' was ruled by a 'Tetrarch'. Each Tetrarch was assisted by a general, two deputy generals, and a judge. Between them, the twelve septs had three-hundred senators who met at assembly each year, although there was no central government.
Greeks and later Romans used the Galatian mercenary forces to wage war. Their notoriety today comes from the epistle of St. Paul to the Galatians in the Bible. They have also been immortalized in the Roman copies of statuary, most famous of these is 'The Dying Gaul'.