(Σέλενκος), king of SYRIA, surnamed PHILOPATOR, was the son and successor of Antiochus the Great. The date of his birth is not mentioned; but he must have already attained to manhood in B. C. 196, when he was left by his father in command of his forces at Lysimachia. in the Chersonese. with orders to rebuild that city, which Antiochus designed, or affected to design, as a royal residence for Seleucus himself (Liv. xxxiii.
On the death of Antiochus III. in B. C. 187, Seleucus ascended the throne without opposition. But the defeat of his father by the Romans, and the ignominious peace which followed it, had greatly diminished the power of the Syrian monarchy, and the reign of Seleucus was, in consequence, feeble and inglorious, and was marked by no striking events. In B. C. 185, we find him sending an embassy to the Achaeans, to renew the friendship and alliance previously existing between them and Antiochus (Plb. 23.4, 9; Diod. xxix. Exc. Legat. p. 622); and shortly afterwards (probably in B. C. 181) assembling a considerable army, to assist Pharnaces, king of Pontus, against Eumenes; but he became alarmed lest his passing Mount Taurus for this purpose should be construed by the Romans into an act of hostility; and, in consequence, abandoned the design and dismissed his forces (Diod. Exc. Vales. p. 576). Yet he did not hesitate to conclude a treaty of alliance with Perseus, whose unfriendly disposition towards the Romans could no longer be a secret, and even to give him his own daughter, Laodice, in marriage, probably in B. C. 178 (Plb. 26.7; Liv. 42.12; Inscr. Del. apud Marm. Arundel. No. 41). But he was still studious to conciliate the favour of the Roman senate, and not long before his death sent his son Demetrius to Rome, to replace his brother Antiochus as a hostage for his fidelity (App. Syr. 45 ; Plb. 31.12). With Egypt lie appears for the most part to have maintained friendly relations; but Ptolemy Epiphanes is said to have been preparing for the invasion of Coele-Syria, when his plans were frustrated by his own death (Hieronym. ad Daniel. 11.20). Towards the Jews the conduct of Seleucus seems to have been, for the most part at least, liberal and favourable : concerning his alleged attempt to plunder the treasury of Jerusalem see HELIODORUS.
After a tranquil and inactive reign of twelve years, Seleucus was assassinated, in B. C. 175, by one of his own ministers, named Heliodorus, who had conceived the design of possessing himself of the sovereign power. The statement of Eusebius that he was sixty years old, is clearly erroneous, as his elder brother Antiochus was not born till B. C. 221. He left two children : Demetrius, who subsequently ascended the throne; and Laodice, married, as already mentioned, to Perseus, king of Macedonia. The name of his wife is unknown; but Froelich supposes him to have married his sister Laodice, the widow of his brother Antiochus. (Appian, Syr. 45, 66 ; Euseb. Arm. pp. 165, 166; Froelich, Ann. Syr. p. 42 ; Clinton, F. H. vol. iii. p. 317.)
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