The defeat of the Egyptian fleet at sea by Antigonus II Gonatus of Macedon enables Antiochos to regain control of the Mediterranean ports lost by his father in the First Syrian War.

Antiochus reconquers much of Anatolia, including the cities of Ephesus and …

…Miletus.

Antiochus having overthrown a tyrant of Miletus after he recaptured the city, the citizens worship him in thanksgiving as a god.

He later organizes an empire-wide cult, as suggested by his epithet, Theos (God).

He also establishes the freedom of the other Ionian cities.

Further, he continues his predecessors' policies of encouraging the foundation of cities in his realm.

The unsuccessful course of Egyptian military operations against the coalition forces of Syria and Macedonia is compensated for, to a certain degree, by the diplomatic skill of Ptolemy, who in 255 first manages to lure Gonatus into concluding a separate peace.

Antigonus wins a naval victory over the fleet of Ptolemy II in 258 BCE.

Whether Gonatus' naval victory of Cos, which secures for him the Aegean Sea and the League of the Islanders, belongs to this (255 BCE) or to the Chremonidean War (261 BCE) is uncertain.

The activity of the Achaean League had initially centered on the expulsion of the Macedonians and the restoration of Greek rule in the Peloponnese.

A single general is substituted in 255, a for the two generals (strategoi) that had previously headed the league.

Gonatus marries his stepbrother Demetrius the Fair to Berenice of Cyrene, thereby establishing Macedonian influence in this neighbor country of Egypt.

The Roman army, commanded by the consul Marcus Atilius Regulus, lands in Africa and begins ravaging the Carthaginian countryside as a result of the favorable outcome of the naval battle off Cape Ecnomus.

The invaders are so successful that the other consul, Lucius Manlius Vulso Longus, is recalled to Rome, leaving Regulus behind to finish the war.

Regulus is at first victorious, winning the Battle of Adys and forcing Carthage to sue for peace.

The terms are so harsh that negotiations fail and, in response, the Carthaginians replace the outmatched general Hamilcar with new leadership in the person of Xanthippus, a Spartan mercenary, to reorganize the army.

Defeating the Roman army and capturing Regulus, along with five hundred of his men, at the Battle of Tunis, Xanthippus then manages to cut off what remains of the Roman army from its base by reestablishing Carthaginian naval supremacy.

The remainder of the army is evacuated by the Roman navy, only to be lost in a storm at sea.

There is no further trustworthy information about Regulus.

According to tradition, he remained in captivity until 250 BCE, when after the defeat of the Carthaginians at the Battle of Panormus he was sent to Rome on parole to negotiate a peace or an exchange of prisoners.

On his arrival, he instead strongly urged the Roman Senate to refuse both proposals and continue fighting, and honored his parole by returning to Carthage where he was executed.

Nicomedes' second wife Etazeta becomes ruler on behalf of her infant sons after his death in 255 BCE.

The grown-up Ziaelas, son of Nicomedes and Ditizele and thus excluded from the throne, had previously fled to Armenia and taken refuge at the court of King Arsames I in Sophene.

On his father's death, he immediately endeavors to regain his rights by force and returns, aided by some Galatians.

Although Etazeta is supported by neighboring cities and Antigonus II Gonatas, Ziaelas rapidly conquers first part, then all of Bithynia, forcing Etazeta and her sons to escape to Antigonus' court in Macedonia about 254 BCE.

Zielas of Bithynia, like his father and his grandfather, also founded a new city named after him, Ziela, but the location of the city is unknown.

He is succeeded by his son Prusias I about 228 BCE after being killed by the Galatian Gauls.