Ptolemy VI Philometor
The guardians of King Ptolemy VI Philometor demanded the return of Coele-Syria in 170 BC, declaring war on the Seleucids on the assumption that the kingdom was divided after Antiochus' murder of his nephew. However Antiochus had prepared more thoroughly and launched a preemptive strike against Egypt, defeating a Ptolemaic force and seizing Pelusium. He then advanced into Egypt proper, conquering all but Alexandria and capturing King Ptolemy. This was partially achieved because Rome (Ptolemaic Egypt's traditional ally) was embroiled in the Third Macedonian War and was not willing to become involved elsewhere.