Antigonus II Gonatas

The combined forces of Pyrrhus, Ptolemy and Lysimachus, assisted by the disaffected among his own subjects, had eventually obliged Demterius to leave Macedonia in 288 BCE.

While Demetrius has been engaged in fighting in Macedonia and Asia Minor, his son Antigonus, as his regent, is engaged in maintaining Macedonian hegemony in Greece, which had been achieved in 287 BCE.

Demetrius has passed into Asia and attacked some of the provinces of Lysimachus with varying success, but falls ill in Cilicia as famine and pestilence destroy the greater part of his army, and he solicits Seleucus' support and assistance.

Before he reaches Syria hostilities break out, and after he has gained some advantages over his son-in-law, Demetrius is totally forsaken by his troops on the field of battle and surrendered to Seleucus.

Antigonus offers all his possessions, and even his own person, in order to procure his father's liberty, but all prove unavailing.

Seleucus now claims the Macedonian kingship.

The Seleucids now control most of the Asian provinces of Alexander’s Macedonian Empire—including most of Anatolia, part of Syria-Phoenicia, Babylonia, Assyria, Media, Parthia, Sogdiana, Bactria, Margiana, Aria, Drangiana, Gedrosia, Carmania, Persis, and Susiana.

Demetrius Poliorcetes dies after a confinement of three years (283 BCE), his captor, Seleucus, having provided enough drink for his rival to do himself in.

His remains are given to his son, Antigonus II Gonatas, and honored with a splendid funeral at Corinth.

Antigonus himself assumes the contested Macedonian kingship on the death of his father. (He will not count the beginning of his reign until 276, however.)

With Demetrius gone, the stage is set for a confrontation between Lysimachus of Thrace and Seleucus.

Antigonus although possessed of only a few bases in Greece after Seleucus' murder in 281, lays claim to Macedonia, which Antiochus disputes.

Ephesus had revolted after the treacherous death of Agathocles, giving the Hellenistic king of Syria and Mesopotamia Seleucus I Nicator in 281 BCE an opportunity for removing and killing Lysimachus, his last rival, at the Battle of Corupedium.

The town again is named Ephesus after the death of Lysimachus, and thus becomes part of the Seleucid Empire.

Macedon again falls into a state of internal confusion, intensified by a coalition of Gallic (Celtic) and Thracian marauders from the north, under the command of Bolgius, who overrun the country.

Ptolemy Keraunus offers battle and is captured and decapitated.

Another band of Gauls under a leader called Brennus (his name may have been the word for “duke”) advances in the autumn of 279 through the emptied Macedonian countryside to Greece.

Brennus suffers heavy losses while trying to break through the Greek defense at the narrow pass of Thermopylae, on the east coast of central Greece.

He eventually finds a way around the pass—in much the same manner as the Persian invaders had done in 480 BCE—but the Greeks escape by sea.

The Gauls sack Delphi, where Brennus is wounded in battle; in the subsequent retreat northward, few Gauls escape.

Brennus avoids capture by committing suicide.

The Aetolians are mainly responsible for driving this major Gallic invasion from the peninsula.

Antigonus, having been almost ruined by the invasion, signs a pact with Antiochus in which each promises not to interfere with the other’s territory.

Antiochus surrenders his claim to Macedon, and hereafter Antigonus' foreign policy will be marked by friendship with the Seleucids.

Bithynia, a region of northwest Anatolia ruled by a local dynasty and never much affected by Phrygian or Persian rule, adjoins the Sea of Marmara, the Bosporus, and the Black Sea, thus occupying an important and precarious position between East and West.

The district had been occupied late in the second millennium BCE by warlike tribes of Thracian origin who harried Greek settlers and Persian envoys alike.

Their remarkable pugnacity had kept them from complete Persian domination after the sixth century; in addition, they never submitted to Alexander the Great or his Seleucid successors.

The small but powerful state has evolved from tribal government to Hellenistic kingship.

Nicomedes, becoming king of Bithynia, in 278, commences his reign by putting to death two of his brothers but the third, subsequently called Zipoetes II, raises an insurrection against him and succeeds in maintaining himself, for some time, in the independent sovereignty of a considerable part of Bithynia.

Meanwhile, Nicomedes is threatened with an invasion from Antiochus, who had already made war upon his father, Zipoetes I, and, to strengthen himself against this danger, he concludes an alliance with Heraclea Pontica and shortly afterwards with Antigonus II Gonatas.

The threatened attack, however, passes over with little injury.

Antiochus actually invades Bithynia but withdraws again without risking a battle.