Ptolemy's aggressions cause continuous friction with Antiochus, who in 279 somehow loses Miletus, in southwestern Asia Minor, to Ptolemy.

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.

Pyrrhus offers peace terms that— according to the Greek historian Appian, writing in the second century CE—would confine Roman power to central Italy, demanding that the Romans halt their aggression against the Greeks of southern Italy and restore the lands they have taken from the Bruttii, Apulians, and Samnites.

When the Senate wavers, Appius Claudius, an aged blind senator, rouses their courage and persuades them to continue fighting.

Aided by the novel use of elephant cavalry, Pyrrhus again defeats the Romans in 279 BCE at Asculum (Ascoli Satriano) in Apulia, although his army again suffers heavy casualties.

His losses in the two battles of Heraclea and Ausculum number seventy-five hundred (almost one-third of his entire force).

When congratulated on his victory, Pyrrhus, according to Plutarch, “replied … that one other such would utterly undo him.” (This type of victory has since been referred to as Pyrrhic victory.)

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.

Arsinoë in about 279 BCE makes her way eventually to Alexandria to advance her fortune.

Soon after her arrival, Ptolemy II's first queen, Arsinoe I, Lysimachus’ daughter, is accused, probably at Arsinoë's instigation, of plotting his murder.

Arsinoe, who has borne Ptolemy three children, including his successor, is nevertheless unable to prevent him from repudiating her and she is exiled to Coptos, a city of Upper Egypt near the Wadi Hammamat.

Pyrrhus sends Cineas to Rome in 278 BCE to renew negotiations on easier terms but these talks, too, are inconclusive.

Cineas then crosses to Sicily to prepare for Pyrrhus' Sicilian campaign.

Pyrrhus follows and, as “king of Sicily,” aids the island's Greeks against Carthage, conquering most of the Punic province except …