Gallic groups, originating from the various La Tène chiefdoms, had begun a southeastern movement into the Balkan peninsula from the fourth century BCE.

Celtic settlements are concentrated in the western half of the Carpathian basin, but there are notable incursions, and settlements, within the Balkan peninsula itself.

The Gallic invasions, originating from their new bases in northern Illyria and Pannonia, climax in the early third century BCE, with the invasion of Greece.

The 279 BCE invasion of Greece proper had been preceded by a series of other military campaigns waged toward the southern Balkans and against the kingdom of Macedon, favored by the state of confusion ensuing from the intricate succession to Alexander.

A part of the invasion crosses over to Anatolia and eventually settles in the area that comes to be named after them, Galatia.