In the late 220s BCE Greece was a patchwork of warring alliances. The two most important powers were Macedonia and the Aetolian League, a confederation of tribal communities and cities centered in Aetolia, a mountainous region north of Nafpaktos. Both sides were anxious should the enemy become too strong. These fears led to the Social War (220-217 BCE), a confusing affair of shifting allegiances and campaigns in western and southern Greece. The war ended unexpectedly when Hannibal defeated the Romans at the Battle of Lake Trasimene. The king of Macedonia, Philip V, wanted to focus on his affairs with Rome, so he signed the peace of Nafpaktos with the Aetolians.