In the meantime, a quarrel had arisen between Ptolemy Philometor and Euergetes Physkon (Livy Epit. 46; Diod. Sic. fr xi), and Gnaeus Octavius, who had been sent to quell the disorder, was assassinated in Syria, while plundering the country. Demetrius, taking advantage of the troubled condition of affairs, consulted with his friend Polybius as to the advisability of attempting to seize the throne of Syria (op. cit. xxxi. 19). The historian advised him not to stumble twice on the same stone, but to venture something worthy of a king, so after a second unsuccessful appeal to the Senate, Demetrius escaped to Tripolis, and from there advanced to Antioch where he was proclaimed king (162 bc). His first act was to put to death young Antiochus, his cousin, and his minister Lysias (Appian, Syriac., c. 47; Ant, XII, x, 1; 1 Macc 7:1-4; 2 Macc 14:1, 2).

As soon as he was established in power, Demetrius made an attempt to placate the Romans by sending them valuable gifts as well as the assassin of Gn. Octavius (Polyb. xxi.23); and he then tried to secure the Hellenizing party by sending his friend BACCHIDES (which see) to make the wicked Alcimus high priest. After a violent struggle and much treachery on the part of Bacchides (Ant., XII, x, 2), the latter left the country, having charged all the people to obey Alcimus, who was protected by an army.

The Jews under Judas resented his presence, and Judas inflicted severe punishment on all who had gone over to Alcimus (1 Macc 7:24). Alcimus, in fear, sent a message for aid to Demetrius, who sent to his assistance Nicanor, the best disposed and most faithful of his friends, who had accompanied him in his flight from Rome (Ant., XII, x, 4). On his arrival in Judea, he attempted to win by guile, but Judas saw through his treachery, and Nicanor was forced to fight openly, suffering two signal defeats, the first at Capharsalama (1 Macc 7:31, 32), and the second (in which Nicanor himself was killed), at Adasa (1 Macc 7:39ff; 2 Macc 15:26ff).

In a short while, however, Demetrius, hearing of the death of Nicanor, sent Bacchides and Alcimus into Judea again (1 Macc 9:1). Judas arose against them with an army of 3,000 men, but when these saw that 20,000 opposed them, the greater part of them deserted, and Judas, with an army of 800, lost his life, like another Leonidas, on the field of battle (1 Macc 9:4, 6, 18). Then Bacchides took the wicked men and made them lords of the country (1 Macc 9:25); while Jonathan, who was appointed successor to Judas, fled with his friends (1 Macc 9:29ff).

During the next seven years, Demetrius succeeded in alienating both the Romans (Polyb. xxxii.20) and his own people, and ALEXANDER BALAS (which see) was put forward as a claimant to the throne, his supporters maintaining that he was the son of Antiochus Epiphanes (1 Macc 10:1-21; Ant, XIII, ii, 1-3). Both Alexander and Demetrius made bids for the support of the Jews, the former offering the high-priesthood and the title of King's Friend (1 Macc 10:20), and the latter freedom from taxes, tributes and customs (1 Macc 10:28ff). Alexander's bait proved more alluring, since the Jews “gave no credence” to the words of Demetrius, and with the aid of the Maccabees, he vied with Demetrius for the space of two years for the complete sovereignty of Syria. At the end of this time, a decisive battle took place, in which Demetrius was slain, and Alexander became king of Syria (150 bc) (1 Macc 10:48-50; Ant, XIII, ii, 4; Polyb. iii.5; see also MACCABEES).

Ptolemy Philometor, whose daughter was the wife of Alexander Balas, now entered into the struggle, and taking Cleopatra, his daughter, from Alexander, he gave her to Demetrius (1 Macc 11:12). He then joined Demetrius' army and the combined forces inflicted a defeat on Balas (145 bc), and from this Demetrius received his surname Nikator (Ant., XIII, iv, 8; 1 Macc 11:14ff).

Jonathan now concluded a favorable treaty with Demetrius, whereby three Samaritan provinces were added to Judea and the whole country was made exempt from tax (1 Macc 11:20-37; Ant, XIII, iv, 9). Demetrius then dismissed his army except the foreigners, thinking himself safe with the loyalty of the Jews assured. In the meantime, Tryphon, one of Balas' generals, set up the son of Alexander, Antiochus, as a claimant to the throne, and secured the assistance of the discarded army of Demetrius. Jonathan's aid was sought and he quelled the rebellion, on condition that the Syrian garrison be removed from Jerusalem (1 Macc 11:41-52; Ant, XIII, v, 2-3).

The king, however, falsified all that he had said, and kept none of his promises, so the Jews, deserting him, took sides with Tryphon and supported the claims of the boy Antiochus (1 Macc 11:53-59; Ant, XIII, v, 5-11 ). Demetrius' generals then entered Syria but were defeated by Jonathan at Hazor (1 Macc 11:63-74), and by skillful generalship he made futile a second attempt at invasion (1 Macc 12:24ff).

After an imprisonment of ten years, he was released and resumed the sovereignty 128 bc, but becoming involved in a quarrel with Ptolemy Physkon, he was defeated in battle at Damascus. From this place, he fled to Tyre, where he was murdered in 125 bc, according to some, at the instigation of Cleopatra, his wife (Josephus, Ant, XIII, ix, 3).

War now broke out in Judea between Alexander Janneus and his Pharisee subjects, who invited Demetrius to aid them. Thinking this a good opportunity to extend his realm, he joined the insurgent Jews and together they defeated Janneus near Shechem (Ant., XIII, xiv, 1; BJ, 1, iv, 5).