At his death in 221 he was followed by his adoptive son, 17-year-old Philip V, who was tutored by the Royal Council (led by Apelles of Chalcis) and the Achaean leader Aratus of Sicyon.

Spurned by his young nephews Scopas and Dorimachus, the strategos Ariston of Trichonion thus tried to prevent the further decay of Aetolia’s international position, and together, the three Trichonians imposed a radical change to Aetolian policy.

Philip V of Macedon appeared reluctant at first, but after Aetolia allied with the Illyrians, he marched south to the Peloponnese, where he gathered the members of the Hellenic League in a council at Corinth.

Although acting as though he was responding to the complaints of the league members, Philip was very interested in war to establish himself as a victorious leader and to consolidate the power of Macedonia in Greece.

The Achaean cities of Dyme, Pharae and Tritaia even refused to pay the due taxes to the League and used the already collected sum to hire a mercenary force of their own.

Starting from Epirus he conquered several cities, including Elaeus and Oeniadae, leading him to Calydon, where he received news of a pending invasion of Macedon by the Dardanians.

Finally he came to terms with the fortress of Samicum, where a combined force of 2,700 Aetolians, Eleans and Spartans including even some Illyrian pirates was only able to negotiate their release on parole.

In the summer of 218 BC, Philip and his allies took a fleet to the island of Cephalonia, but when the siege of Pale failed, the king decided on an attack against the Aetolian heartland.

So he moved his army by ship to the Gulf of Ambracia and from there marched past the city of Stratos and the Trichonis-Lake to Thermon, devastating the temples and statues in the Pan-Aetolian sanctuary.

From the Gulf of Ambracia Philip sailed back to Corinth and then quickly marched to Sparta, where he made many successful raids against the unfortified villages south of the city as far as the port of Gythium.

When the Spartan king Lycurgus tried to block his path north, Philip and Demetrius of Pharos dislodged the Lacedaemonians from the Menelaion above the city, while Aratus led the main force to cross the Eurotas River.

Advised by Demetrius of Pharos, who hoped to regain possession of his former kingdom, the Macedonian king decided to end the war with Aetolia in order to focus his attentions on Rome.

The poor performance of the Achaean forces and the limited engagement of the minor allies, however, led to a significant shift in the internal balance of powers towards the Macedonian hegemon.

As a result of Philip's ability the Kingdom of Macedon became the major military power in Greece, but at the same time his growing ambition threatened to damage the cohesion of the Symmachy as intended by his stepfather and his former tutor.