The Second Illyrian War lasted from 220 BC to 219 BC. In 219 BC, the Roman Republic was at war with the Celts of Cisalpine Gaul, and the Second Punic War with Carthage was beginning. These distractions gave Demetrius the time he needed to build a new Illyrian war fleet.[citation needed] Leading this fleet of 90 ships, Demetrius sailed south of Lissus, violating his earlier treaty and starting the war.
Demetrius' fleet first attacked Pylos where, he captured 50 ships after several attempts. From Pylos the fleet sailed to the Cyclades, quelling resistance they found on the way. Demetrius foolishly sent a fleet across the Adriatic, and, with the Illyrian forces divided, the fortified city of Dimale was captured by the Roman fleet under Lucius Aemilius Paulus. From Dimale the navy went towards Pharos. The forces of Rome routed the Illyrians and Demetrius fled to Macedon where he became a trusted councilor at the court of Philip V of Macedon, and remained until his death at Messene in 214 BC.