Aetolian League
Earlier in 231 BC, after the dissolution of the Epirote League, the Aetolian League had requested the city of Medion to join it, but the Acarnanians refused. The Aetolians decided to take Medion by force, beginning the siege in June. The king of Macedon Demetrius II Aetolicus, a rival of the Aetolian League, being himself engaged against the Dardanians, requested Agron of Illyria to intervene and help the Acarnanians. Agron accepted and sent a fleet of 100 "lembi" and 5,000 men to Medion. This was the largest force any Illyrian king had ever assembled. The Illyrians and Macedon were not necessarily allied, but the former was instead hired to assault the Aetolians at Medion as mercenaries for the latter.