BC Scerdilaidas entered into an alliance with Philip V of Macedon. Scerdilaidas had aided Philip during the Social War against the Spartans but this produced little profit for him. Scerdilaidas' support for Macedon against the Aetolians was curtailed by 'plots and conflicts' caused by rulers of various cities. In 217 BC, Scerdilaidas ceased his support for Philip V, maintaining that a promised subsidy was unpaid and long overdue. He dispatched 15 ships, ostensibly to collect and escort the payment, but at the island of Leucas south of Corcyra his forces killed two of Philip's Corinthian allies and seized their four ships. Scerdilaidas' fleet then sailed south and began to plunder shipping around Cape Malea in the southern Peloponnese. In response, Philip prepared a strong naval force of twelve decked ships, eight open vessels and thirty hemioliae, which headed south at full speed to deal with Scerdilaidas. This counterattack by Philip was too slow and missed its targets. Scerdilaidas went on to march into Dassaretia, taking several cities and invading parts of western Macedonia. He looted Pissaeum in Pelagonia and overran some frontier districts of Macedon. Before the winter Philip had occupied the area of Lyncestis, cutting off the direct route from Illyria, and extended his power to Dassaretia. Philip was planning an invasion of Illyria. However, in doing so, he would face not only the lembi of Scerdilaidas, but also the heavier warships of the Roman navy. First Macedonian War Scerdilaidas soon entered into an alliance with Rome. Influenced by Demetrius, Philip's first target was the Illyrian coast. In 216 BC he had built a fleet of one hundred light warships, using Illyrian shipwrights. He led his fleet around the Peloponnese into the Adriatic, gambling that Rome, deeply involved in the Hannibal crisis, would not intervene. Scerdilaidas appealed for help and the Romans sent ten heavy quinqueremes from Sicily. Philip fled and the invasion of Illyria was avoided for the moment. Twice thwarted in attempts at invasion of Illyria by sea, and now constrained by Laevinus' fleet in the Adriatic, Philip spent 213 BC and 212 BC making advances in Illyria by land. Keeping clear of the coast, he took the inland towns of Atintania and Dimale, and subdued the tribe of the Dassaretii and the Illyrian Parthini and the southern part of the Ardiaean State. Scerdilaidas, with his son Pleuratus III, Longarus of the Dardanian State and Epirus, together