At length the Roman general was helped out of his perplexity by the treachery of some men of rank among the Epirots--who were otherwise well disposed to Macedonia--and especially of Charops.

They conducted a Roman corps of 4000 infantry and 300 cavalry by mountain paths to the heights above the Macedonian camp; and, when the consul attacked the enemy's army in front, the advance of that Roman division, unexpectedly descending from the mountains commanding the position, decided the battle.
Philip lost his camp and entrenchments and nearly 2000 men, and hastily retreated to the pass of Tempe, the gate of Macedonia proper.
He gave up everything which he had held except the fortresses; the Thessalian towns, which he could not defend, he himself destroyed; Pherae alone closed its gates against him and thereby escaped destruction.

The Epirots, induced partly by these successes of the Roman arms, partly by the judicious moderation of Flamininus, were the first to secede from the Macedonian alliance.

On the first accounts of the Roman victory the Athamanes and Aetolians immediately invaded Thessaly, and the Romans soon followed; the open country was easily overrun, but the strong towns, which were friendly to Macedonia and received support from Philip, fell only after a brave resistance or withstood even the superior foe--especially Atrax on the left bank of the Peneius, where the phalanx stood in the breach as a substitute for the wall.

Except these Thessalian fortresses and the territory of the faithful Acarnanians, all northern Greece was thus in the hands of the coalition.
The Achaeans Enter into Alliance with Rome The south, on the other hand, was still in the main retained under the power of Macedonia by the fortresses of Chalcis and Corinth, which maintained communication with each other through the territory of the Boeotians who were friendly to the Macedonians, and by the Achaean neutrality; and as it was too late to advance into Macedonia this year, Flamininus resolved to direct his land army and fleet in the first place against Corinth and the Achaeans.