Demetrius Poliorcetes (taker of cities, from Gr. to besiege), a king of Macedonia, born about 338 B. 0., died in 283. He was the son of Antigonus, who in the first division of the Macedonian empire received several provinces of Asia Minor for his share. In the wars of his father against Eumenes and Ptolemy, Demetrius early exhibited valor and skill. Commanding in Syria, he was defeated by Ptolemy in the battle of Gaza (312 B. C), but soon restored the balance of the war by a victory over one of his generals. A treaty of peace was concluded soon after, but was of short duration. More decisive were his services to his father in the expedition to Greece, the most important places of which had been occupied and garrisoned by Cassander, son of Antipater of Macedon. Sailing from Ephesus to Athens in 307, Demetrius entered without resistance the harbor of the Piraeus with his fleet, which was mistaken for that of Egypt. Demetrius Phalereus, who had ruled Athens ten years in allegiance to Macedon, was compelled to retire to Thebes; Munychia and Me-gara, defended by garrisons in the interest of Cassander, were unable to withstand the besieger, and finally he triumphantly entered Athens. Having announced the restoration of the ancient democratic institutions, and promised distributions of corn and ship timber, he was received as god and saviour by the people. Summoned to the assistance of his father in his war against Ptolemy in Cyprus, he crossed over to that island, defeated the Egyptian fleet, and made himself master of all Cyprus; after which both he and his father assumed the title of king, and their example was followed by Ptolemy, Lysimachus, and Seleu-cus, the rival potentates of Egypt, Thrace, and Syria. Demetrius, with his father, next undertook an invasion of Egypt by sea and land, which failed, their forces being repulsed with great loss. He next (305) besieged Rhodes for more than a year; but the Rhodians, aided by the allied enemies of his father, withstood bravely, and the siege was terminated by a treaty. Demetrius then sailed to Greece, compelled the Boeotians to relinquish their alliance with Msfce-don, expelled Cassander from Attica, and made himself master of Corinth, Argos, Sicyon, and most of the towns of Arcadia. In Athens the deified deliverer was received with the wonted honors, and resided as the guest of Minerva in the Parthenon, which he polluted by shameless debauchery.
Again summoned to aid his father, he hastened to Asia, and fought in the great battle of Ipsus, in Phrygia (301), which ended in his defeat and the death of Antig-onus, whose dominions were broken up, the greater part falling into the hands of Seleucus. Demetrius, embarking with the remnant of his army for Athens, met envoys from that city who announced that he would not be admitted. This defection was followed by the loss of his other possessions in Greece. He however gave Seleucus his daughter Stratonice in marriage, and made with him a treaty of alliance which stipulated that Demetrius should retain possession of Oilicia, Cyprus, and a part of the coast of Syria. He now armed for the reconquest of Greece, took Athens after a long resistance (295), and made a successful expedition into the Peloponnesus, when his attention was turned to Macedon. Antipater and Alexander, the surviving sons of Cassander, were engaged in a bloody struggle for the throne, and the latter invoked the aid of both Demetrius and Pyrrhus of Epirus. Pyrrhus appeared first and vanquished Antipater; Demetrius came after him, and deprived Alexander of both his throne and his life (294). Meanwhile his possessions in Asia were taken by Ptolemy and Seleucus. The following four years were occupied by two sieges of Thebes, an invasion of Thrace, and a war with Pyrrhus and the AEtolians, after the termination of which he was preparing for a new campaign in Asia when he was attacked (287) by a triple invasion from Thrace, Epirus, and Egypt. While marching against the Epirotes he was deserted by his Macedonian troops, who proclaimed Pyrrhus king.
Demetrius escaped to his son Antigonus Gonatas, who had maintained possession of Greece, and saved a part of his dominion by a treaty with Pyrrhus. Leaving his son in Greece, he crossed over to Miletus, and fought his way as far as the northern mountain range of Syria, but was finally compelled to surrender to Seleucus, who confined him at Apamea in Syria till his death.