Attalus has by 221 BCE lost to Achaeus most of the Anatolian territory gained from the Seleucids.

Aratus, on the accession of Philip V in 221 BCE, counters Aetolian aggression by obtaining the assistance of the Hellenic League.

Hasdrubal the Fair, having, with his father-in-law Hamilcar Barca, revived Carthaginian power through expansion in Spain for the past fifteen years, is killed in 221 by a Celtic assassin.

Hannibal, son of Hamilacar, is proclaimed commander-in-chief by the army and confirmed in his appointment by the Carthaginian government.

Molon has meanwhile marched west against the Seleucids, but when Antiochus III moves against him from Syria, Molon's forces desert him, and the revolt ends with the rebel governor's defeat in 220 BCE on the far bank of the Tigris.

(This two-year period is the sole time that the Seleucid kings have lost control of Mesopotamia.)

Antiochus also conquers Atropatene, the northwestern part of Media.

Shortly hereafter, Antiochus has Hermeias killed and is thus rid of most of the influences from the previous By 220 BCE, Antiochus has put down most of the rebellions, but Achaeus will not be defeated until 213 BCE.

Prusias fights a war against Byzantium in 220 BCE, then defeats the Galatians who his grandfather, Nicomedes I, had invited across the Bosporus.

The Delphic oracle establishes a festival in Magnesia to honor the goddess Artemis, who reportedly appears there in 220.

The architect Hermogenes of Priene erects the Temple of Artemis Leukophryena in Magnesia to commemorate her appearance; a sculptured frieze depicting an Amazonomachy decorates the building.

The geographer Strabo mentions this temple, the third greatest temple after those in Didyma and Ephesus, but considered finest of all for its proportions.

Demetrius of Pharos (the island of Hvar in present Croatia), now Illyria’s leading ruler, in 220 raises a fleet of ninety lembi, or lemboi (native ships of the Illyrians, lacking rams but possessing wider beams than typical warships of the day) and sails south of Lissus, in violation of the treaty of 228 with Rome, resuming piracy.

Demetrius makes several unsuccessful attacks on Pylos; then, taking fifty of the ships, …

…begins pillaging the Cyclades (Polybius, III.16.3-4).

Classical writers depict Ptolemy IV as a drunken, debauched reveler, completely under the influence of his disreputable associates, among whom Sosibius is the most prominent.

Cleomenes, imprisoned by Ptolemy, escapes in 219 and, after failing to raise a revolt in Alexandria, takes his own life.