After the Peace of Naupactus in 217 BC, Philip V tried to replace
Roman influence along the eastern shore of the
Adriatic. He first tried to invade
Illyria from the sea, but with limited success. His first expedition in 216 BC had to be aborted, while he suffered the loss of his whole fleet in a second expedition in 214 BC. A later expedition by land met with greater success when he captured
Lissus in 212 BC.
In 215 BC he entered into a treaty with
Hannibal, the
Carthaginian general then in the middle of an invasion of Roman Italy. Their treaty defined spheres of operation and interest, but achieve little of substance or value for either side.
Philip became heavily involved in assisting and protecting his allies from attacks from the
Spartans, the Romans and their allies.
Rome's alliance with the
Aetolian League in 211 BC effectively neutralised Philip’s advantage on land. The intervention of
Attalus I of Pergamum on the Roman side further exposed Philip's position in Greece.
Philip was able to take advantage of the withdrawal of Attalus from the Greek mainland in 207 BC, along with Roman inactivity and the increasing role of
Philopoemen, the
strategos of the
Achaean League. After sacking Thermum, the religious and political centre of
Aetolia, Philip was able to force the Aetolians to accept his terms in 206 BC. The following year he was able to conclude the
Peace of Phoenice with Rome and its allies.