The ambitious Philip V of Macedon, now popular throughout much of Greece following his decisive actions in the so-called War of the Allies (also the Social War of 219—217), looks to extend his empire while Rome is preoccupied with fighting Carthage in the Second Punic War.

In an attempt to stem the tide of Roman expansion, sets out to attack Rome's client states in neighboring Illyria.

He confirms his purpose in 215 by making an alliance against Rome with Hannibal, the Carthaginian general who is invading Italy and is interested to protect supply lines from North Africa.

Philip, currently the most powerful ruler in the Balkans, thus initiates ten years of inconclusive warfare against Rome (First Macedonian War, 215-205).

Rome responds by supporting Philip's many enemies in the Balkans as they fight the war, which expands Roman interests into the Balkans.