The decisive blow came, however, earlier than Flamininus had hoped.

Philip, impatient and confident as he was, could not endure to await the enemy on the Macedonian frontier: after assembling his army at Dium, he advanced through the pass of Tempe into Thessaly, and encountered the army of the enemy advancing to meet him in the district of Scotussa.
The Macedonian and Roman armies--the latter of which had been reinforced by contingents of the Apolloniates and the Athamanes, by the Cretans sent by Nabis, and especially by a strong band of Aetolians--contained nearly equal numbers of combatants, each about 26,000 men; the Romans, however, had the superiority in cavalry.
In front of Scotussa, on the plateau of the Karadagh, during a gloomy day of rain, the Roman vanguard unexpectedly encountered that of the enemy, which occupied a high and steep hill named Cynoscephalae, that lay between the two camps.

Driven back into the plain, the Romans were reinforced from the camp by the light troops and the excellent corps of Aetolian cavalry, and now in turn forced the Macedonian vanguard back upon and over the height.

But here the Macedonians again found support in their whole cavalry and the larger portion of their light infantry; the Romans, who had ventured forward imprudently, were pursued with great loss almost to their camp, and would have wholly taken to flight, had not the Aetolian horsemen prolonged the combat in the plain until Flamininus brought up his rapidly-arranged legions.

The king yielded to the impetuous cry of his victorious troops demanding the continuance of the conflict, and hastily drew up his heavy-armed soldiers for the battle, which neither general nor soldiers had expected on that day.