Greece was now permitted to enjoy another short interval of repose, while Philip returned to Macedonia, where his presence was needed to protect his north-west frontier against the inroads of Scerdilaidas. He was fully occupied in this quarter during the rest of the summer of 217, and in the ensuing winter he increased his navy with 200 new galleys built on the Illyrian model. In the spring he embarked his forces, and sailed round Peloponnesus into the Adriatic. Though Italy was uppermost in his thoughts, so as to haunt his dreams, he thought it necessary, before he crossed the channel, to secure his dominions more effectually against Scerdilaidas, and for this purpose resolved to make an expedition to the coast of Illyria. He expected, it seems, that the Romans would send succours to Scerdilaidas, as in fact the Illyrian, when he heard of Philip's maritime preparations, had requested them to do; and he therefore waited for some time between Cephallenia and Leucas, to ascertain the movements of the Roman fleet. But having learnt that it was still at Lilybæum, he sailed up toward Apollonia, and had anchored near the mouth of the Aous, when he received advice that Roman galleys had been seen at Rhegium bound for Apollonia. Believing that the whole Roman fleet was at hand, he gave immediate orders for retreat, and, as if chased by a victorious enemy, pushed forward day and night until he reached Cephallenia.