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.

…Lilybaeum (Marsala).

Nicomedes, more against his brother than his foreign enemies, now calls in the assistance of more powerful auxiliaries and enters into an alliance with the warlike Celts, or Gauls, who, under Leonnorius and Lutarius, had arrived on the opposite side of the Bosporus and are, at this time, engaged in the siege of Byzantium, 277 BCE.

Three Gallic tribes, twenty thousand strong, are initially recruited.

Having furnished them with the means of crossing into Asia, he first turns the arms of his new auxiliaries against Zipoetes II, whom he defeats and puts to death, and thus reunites the whole of Bithynia under his dominion.

Of the events that follow we have little information.

It is probable that the Celts subsequently assisted Nicomedes against Antiochus, but no particulars are recorded, either of the war or the peace that terminated it.

It appears, however, that Nicomedes was left in the undisturbed possession of Bithynia, which he continues to govern from this time until his death and which is to rise to a high degree of power and prosperity during his long and peaceful reign.

Antiochus, preoccupied with the pacification of Syria following the Gallic incursions in Greece, encourages Greek immigration to his realm and establishes many new cities in Asia Minor to serve as counterweights to the Gauls.

The Gauls, after discharging their military service to Bithynia, have by 276 settled in parts of Phrygia but continue to ravage and plunder on their own.

The deposed queen’s ambitious rival, widow to both Lysimachus and Keraunus, marries Ptolemy and adopts her children.

Sibling marriage, while scandalous to the Greeks, is a customary practice in Egypt.

The event shocks Greek public opinion but is celebrated by the Alexandrian court poets.

Philadelphoi (“Brother-Loving”) consequently is added to the names of Ptolemy and Arsinoe II.

Ptolemy, taking advantage of the difficulties of the rival kingdoms of the Seleucids and Antigonids, extends his rule in Syria, Asia Minor, and the Aegean at their expense and asserts at the same time his influence in Ethiopia and Arabia.

Egyptian embassies to Rome as well as to India reflect the wide range of Ptolemy's political and commercial interests.

The Egyptians invade northern Syria in 276, but Antiochus defeats Ptolemy, repels him, and secures an alliance with Ptolemy’s half brother, who rules Cyrene.

Macedon has had no central government for the past two years: three men had been offered the crown, but two of them were immediately dethroned and the third one, a nobleman named Sosthenes, had refused the supreme power.

Although the city-dwellers have had to fend for themselves, the Gauls lack the capacity to besiege towns.

Sosthenes has been able to harass Bolgius, who has returned with his loot to the region of modern Serbia.

The Macedonians in 276 acknowledge Antigonus king.

The despotic methods employed by Pyrrhus provoke a revolt of the Greek Sicilians, and in 276 (or early 275), he returns to Italy.

On his departure, the Syracusans appoint as commander of the troops his supporter Hiero, who strengthens his position by marrying the daughter of Leptines, the city's leading citizen.

Ptolemaic Egypt invades northern Syria in 276 BCE, but Antiochus defeats Ptolemy, repels him, and secures an alliance with Ptolemy’s half brother, who rules Cyrene.