by Celts. It may therefore be that Seuthopolis was not destroyed by the Celts, but by the Seleucid king Antiochus II, who campaigned in the Thracian interior in around 252. The Odrysians after 250 BC Most modern historians believe that the Odrysian kingdom continued to exist throughout the Hellenistic and the early Imperial period, when it became a Roman vassal state. However, the evidence for this assumption is in fact very slim. Throughout the remainder of the 3rd century, Thrace remained fragmented into various political entities. In the interior ruled various badly known Thracian dynasts. In the east was the kingdom of Tylis, a Celtic-dominated predator state which existence was based on blackmailing tribute and that was eventually destroyed by a Thracian revolt or attack soon after 220. In the southeast and based at the town of Lysimachia, the Seleucids established themselves under Antiochus II (r. 261–246), who relied on allied Thracian dynasts to expand his influence deep into the interior. After his death in 246 the Seleucid presence was replaced by that of the Ptolemies, who established a satrapy in coastal Thrace. An Odrysian kingdom, however, is not described in the sources. In the last years of the 3rd century, Macedonia under king Philip V began a renewed expansion to the east, exploiting the weakness of the Ptolemies after the death of Ptolemy IV. While Philip's initial focus was on coastal Thrace, he also led a campaign into the interior. Temporarily losing his Thracian holdings after the end of the Second Macedonian War in 197, he reconquered most of them a decade later, while again campaigning in the Thracian interior. In 184 or 183 he pushed into the plains of the upper Hebros, defeated the Odrysians and other local tribes and conquered Philipopolis, although the Odrysians reconquered the town soon afterwards. It may be noteworthy that no Odrysian king is mentioned. While in 181, Philip was still climbing the Haemus in northern Thrace, his Thracian empire collapsed with his death two years later. Between 171 and 168, Philip's heir Perseus engaged the Roman Republic in the Third Macedonian War. Perseus' most trusted ally in this war was the Thracian king Cotys, whom the historian Polybius calls an Odrysian. He fought in the battles of Callinicus and Pydna, but eventually became a Roman ally after the war. Perhaps he is identical with the Cotys mentioned by the historian Strabo. However,