Seleucid ambitions to occupy Coilē-Syria, which received a setback at Raphia, revived after the death of Ptolemy IV Philopator in 204 B.C. Under Ptolemy's infant son, the Egyptian court soon sank into an atmosphere of intrigue which facilitated the Seleucid invasion southwards in 202 B.C. (Polyb. 15.20; Hieron. In Dan. 11.13–14). Antiochus III failed to occupy Gaza, the last Ptolemaic stronghold in southern Palestine, during 201 B.C. (Polyb. 16.22a), and in winter of 201–200 B.C. he retired to Syria after setting up garrisons in key positions (see Map 10). The Ptolemies, however, did not give up: supported by new recruits from Greece (Polyb. 15.25.16; Livy 31.43.5–7), Scopas, the Aetolian officer serving as chief of staff in the Ptolemaic army, reoccupied Coilē-Syria in the winter of 200 B.C. (Jos. Ant. 12.131, 135; Hieron. loc.cit.). Antiochus' counterattack probably took place the following summer. The Egyptian army tried in vain to halt the enemy near the northern frontier, at Panion, and was defeated and scattered. Scopas himself, with 10,000 survivors, took refuge in Sidon (Hieron. op.cit. 15–16, based on Porphyrios), probably in the hope of being evacuated by sea, but the Egyptian navy seems to have been delayed, and Scopas had to surrender to Antiochus' besieging force. Thus the long struggle in Coilē-Syria was decided ultimately in favour of the Seleucids.

Unfortunately, the only extant account of the battle is an indirect report which has survived in the sixteenth book of Polybius (par. 18–19). Berating Zeno of Rhodes for what he calls his preference for rhetorical phraseology over historical accuracy, Polybius tries to illustrate his argument by criticizing the version presented by Zeno of the battle of Panion.