Ptolemy, adhering to a defensive foreign policy,…

The mostly coastal cities of Aetolia, a district of Greece that lies north of the Gulf of Corinth and is bordered on the east by Mount Oxya and on the west by the Achelous River, had formed the Aetolian League in the fourth century BCE.

Now a strong confederacy, the league, having successfully resisted invasions by Macedon in 322 and 314-311, has rapidly grown in strength during the ensuing period of Macedonian weakness, …

…expanding into Delphi (center of the Amphictyonic Council) and …

…allying with Boeotia in about 290 BCE; the Aetolian League will become a major opponent of Macedon and of the soon-to-be-reconstituted Achaean League.

The exhausted Samnites finally conclude a peace in 290 BCE with the Romans, who allow their valorous opponents to become Roman allies, not subjects, as civitas sine suffragio.

The Romans are now the dominant power in Italy.

Agathocles' reign as king in Sicily has been peaceful, allowing him to enrich Syracuse with many public buildings.

Dissension among his family about the succession, however, causes him in his will to restore liberty to the Syracusans, and his death in 289 is followed by a recrudescence of Carthaginian power in Sicily.

The unpopular Demetrius, after ruling for six years in Macedon, is in 288 ousted by Lysimachus in alliance with Pyrrhus, who has continually taken advantage of Demetrius’s occasional absence to ravage the defenseless part of his kingdom, taking Thessaly and the western half of Macedonia.

The Egyptian fleet participates decisively in the liberation of Athens from Macedonian occupation in the final coalition war between Alexander’s successors, in which Ptolemy, Seleucus, Lysimachus, and Pyrrhus oppose Demetrius.

The death of Agathocles has left idle and unemployed in Sicily a body of Campanian mercenaries who had been in his hire.

Most of them return home but some, liking the climate and the prospect of adventure on a foreign island, remain.

These desert from Syracuse and enter the walled Greek stronghold of Messana (Messina, in northeastern Sicily).

The inhabitants, a peaceful people, allow into their homes the traveling mercenaries, who, after a time, become restless and plot to capture the town.

One night the mercenaries betray their hosts and kill most of the population who are unprepared, in this way claiming Messana for themselves.

The surviving Messanian men are expelled and the property and women divided.

After their victory, the mercenaries name themselves the Mamertines after the Oscan war-god Mamers.

Transforming a bustling town of farmers and traders into a raiding base, they plunder the surrounding territory.

Demetrius, deposed from the throne of Macedon, passes into Asia in 287 and attacks some of the provinces of Lysimachus with varying success.

Famine and pestilence destroy the greater part of his army, and he solicits the support and assistance of Seleucus.

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

Agathocles in 287 BCE is sent by his father against Demetrius I Poliorcetes, who has marched into Anatolia to deprive Lysimachus of Lydia and Caria.

He is successful in this expedition, defeating Demetrius I and driving him out of his father's provinces.