Answer
The Ptolemaic Kingdom successfully defended its territories from the early campaigns of Antiochus III, an ambitious Seleucid ruler who sought to expand his empire in the 3rd century BCE. Antiochus's failure to conquer the Ptolemaic Kingdom can be attributed to the strength of the Ptolemaic military and the strategic alliances they formed with other Hellenistic kingdoms, which effectively deterred Antiochus from achieving his expansionist goals.