Antigonus III Doson
The Achaean League managed to capture Megalopolis in 235BC, and by the end of DemetriusII's reign most of the Peloponnese except Argos was taken from the Macedonians. DemetriusII also lost an ally in Epirus when the monarchy was toppled in a republican revolution. DemetriusII enlisted the aid of the Illyrian king Agron to defend Acarnania against Aetolia, and in 229BC, they managed to defeat the combined navies of the Aetolian and Achaean Leagues at the Battle of Paxos. Another Illyrian ruler, Longarus of the Dardanian Kingdom, invaded Macedonia and defeated an army of DemetriusII shortly before his death in 229BC. Although his young son Philip immediately inherited the throne, his regent Antigonus III Doson (), nephew of AntigonusII, was proclaimed king by the army, with Philip as his heir, following a string of military victories against the Illyrians in the north and the Aetolians in Thessaly.