The War of the Diadochi (322–275 BCE), was a protracted series of conflicts between Alexander’s generals (and eventually their sons) over the control of his vast empire. In 281 BCE, a vast alliance of Celtic tribes exploited the instability to invade Greece defeating and killing the ruling Diadoch heir, Ptolemy Ceraunus, before in turn being defeated by another heir, Antigonus Gonatas. Thereafter, the Celtic horde dispersed. Some formed the kingdom of Tylis in Thrace, others answered the call for mercenaries from the Bithynian king, Nicomedes. Three tribes, the Trocmii, Tectosages and Tolistobogii, made the journey to Bithynia, rampaging through the territory of another Diadoch heir, the Seleucid Antiochus I, who used war elephants to defeat them (275 BCE). The Celts settled in Galatia, establishing a tribally based canton system, acting as mercenaries for hire and periodically raiding their neighbours before final defeat – and subsequent subjugation – by the Romans at Mount Olympus (189 BCE).
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