The course of this war is very unclear, with the chronological and causal relationship of events attested at different times and in different theatres being open to debate. Between 259 and 255 BC, the Ptolemaic navy, commanded by Chremonides, was defeated in a sea battle at Ephesus. Antiochus II then took control of the Ptolemaic cities in Ionia: Ephesus, Miletus, and Samos. Epigraphic evidence shows that this was complete by 254/3 BC. Ptolemy II himself invaded Syria in 257 BC. We do not know what the outcome of this invasion was. At the end of the war, Ptolemy had lost sections of Pamphylia and Cilicia, but none of the Syrian territory south of the Eleutheros River. It is possible, but not certain, that Antigonus was still at war with Ptolemy II during this period and that his great naval victory over Ptolemy at the Battle of Kos (mentioned above) took place in 255 BC within the context of the Second Syrian War.
The course of this war is very unclear, with the chronological and causal relationship of events attested at different times and in different theatres being open to debate. Between 259 and 255 BC, the Ptolemaic navy, commanded by Chremonides, was defeated in a sea battle at Ephesus. Antiochus II then took control of the Ptolemaic cities in Ionia: Ephesus, Miletus, and Samos. Epigraphic evidence shows that this was complete by 254/3 BC. Ptolemy II himself invaded Syria in 257 BC. We do not know what the outcome of this invasion was. At the end of the war, Ptolemy had lost sections of Pamphylia and Cilicia, but none of the Syrian territory south of the Eleutheros River. It is possible, but not certain, that Antigonus was still at war with Ptolemy II during this period and that his great naval victory over Ptolemy at the Battle of Kos (mentioned above) took place in 255 BC within the context of the Second Syrian War.