The Chremonidean war continues.

Although the Egyptian fleet in 265 has blockaded the Saronic Gulf, Gonatus defeats Areus near Corinth.

The Mamertini appeal for and receive troop support from the Carthaginians when Hiero II of Syracuse blockades Messana in around 265 BCE.

Nicomedes of Bithynia, in imitation of his father, and so many others of the Greek rulers of Asia, determines to perpetuate his own name by the foundation of a new capital, placed by Eusebius in 264 BCE.

The site that he chooses, in the immediate neighborhood of the Megarian colony of Astakos, is so judiciously selected that the city of Nicomedia will continue for more than six centuries to be one of the richest and most flourishing in Anatolia.

The Macedonians repel an Epirote invasion in 264 BCE.

Gurges’ successor, Marcus Valerius Flaccus, after receiving the surrender of Volsinii through its starvation in 264, razes the town and executes the leaders of the plebeian party.

The first display of gladiators at Rome in 264 is believed to have featured now-captive freedmen from Volsinii.

The Romans rescue and restore the remaining Etruscans of Volsinii, but decide it is necessary to remove them from that location to a new city on the shore of Lake Bolsena.

The new city has none of the natural defenses of the old and is not in any way sovereign.

The portable wealth from the old city is carried off to Rome.

If the old city was in fact Orvieto, it cannot have remained unoccupied for long; however, it is never again to be a threat to Rome.

The new city soon assimilates to Roman culture, including language.

Rome, in consolidating its control of southern and central Italy, plants Roman and Latin military colonies on confiscated lands.

They award complete Roman citizenship only to some cities and tribes as a way of rewarding them for rapid romanization and faithfulness to Rome.

The Romans impose limited citizenship on other cities and tribes, forcing them to conclude a perpetual alliance with Rome and to provide soldiers for Roman wars, and depriving these cities of an independent foreign policy.

In 264 BCE, Roman Italy comprises about fifty-two thousand square miles (one hundred and toirty five thousand square kilometers), populated by two hundred and ninety two thousand Roman (male) citizens, and about seven hundred thousand Roman allies.

Gladiators—professional combatants drawn from the ranks of prisoners of war, criminals, enslaved people, and volunteer freedmen—compete from 264 as public entertainment as part of memorial ceremonies in Rome.

Roman expansion to the Straits of Messana (Messina), and Carthaginian occupation of Messana itself in 264 triggers a war between Rome and Carthage (later known as the first Punic War, from punicus, meaning "Carthaginian," after Punt, the Roman name for the Carthaginians’ original homeland of Phoenicia).

Allied Greek cities in southern Italy feel their commerce threatened, many Romans fear any powerful neighbor in Sicily, some aristocrats desire military glory, and many voters want plunder.

Although opinion in the Roman Senate is divided, the Roman Assembly honors a Messanian request for intervention.

The Carthaginians initially withdraw, then counterattack with aid from Hiero II, who, when Rome sides with the Mamertini, allies Syracuse with Carthage.

The Mamertini, in a sudden reversal, spurn Carthage when Hiero again attacks Messana in 264 BCE: calling on the Romans for aid, they accept forces from Rome.

The gathering of the two rival intervening armies precipitates a general war, known as the First Punic War.

Hiero at once joins the Carthaginian leader Hanno, who has recently landed in Sicily, but the Roman consul Appius Claudius defeats them, and …

…Hiero withdraws to Syracuse.

Antigonus’ forces besiege Athens in 263 BCE following the departure of the Egyptian fleet blockading Macedon.