222 BC

Events

Mediolanum (modern Milan), stronghold of the Gallic tribe of the Insubres (led by Viridomarus), falls to Roman legions in Lombardy (led by consul, Marcus Claudius Marcellus), in the Battle of Clastidium. Marcus Claudius Marcellus personally slays the chief, Viridomarus. This victory removes the Gallic threat to Rome. Marcellus wins the spolia opima ("spoils of honour"; the arms taken by a general who kills an enemy chief in single combat) for the third and last time in Roman history.

Cleomenes III of Sparta is defeated in the Battle of Sellasia (north of Sparta) by Antigonus III and his allies, the Achaean League and the Illyrians (under the command of Demetrius of Pharos), and flees to Egypt under the protection of King Ptolemy III. Antigonus III's forces occupy Sparta, which is the first time this city has ever been occupied.
Almost all of Greece falls under Macedonian suzerainty after Antigonus III re-establishes the Hellenic Alliance as a confederacy of leagues, with himself as president.

The Seleucid forces under their general Achaeus succeed in winning back from Pergamum all the Seleucid domains in Anatolia lost six years earlier.
Mithridates II of Pontus gives his daughter Laodice in marriage to the Seleucid king Antiochus III. Another of his daughters, also named Laodice, is married about the same time to Achaeus, a cousin of Antiochus.

The state of Qin conquers the state of Yan and defeats the last defensive forces of the state of Zhao.