Titus Livius (Livy), The History of Rome, Book 32
Cyrus Evans, Ed.

12. On the third day, the Roman party made the signal by smoke, to notify that they had gained possession of the eminence to which they had been directed; and then the consul, dividing his forces into three parts, marched up with the main strength of his army, through a valley in the middle, and made the wings on right and left advance to the camp of the enemy. [2] Nor did these advance to meet him with less alacrity. The Roman soldiers, in the ardour of their courage, long maintained the fight on the outside of their works, for they had no small superiority in bravery, in skill, and in the nature of their arms; [3] but when the king's troops, after many of them were wounded and slain, retreated into places secured either by intrenchments or situation, the danger reverted on the Romans, who pushed forward, inconsiderately, into disadvan- [p. 1407]tageous grounds and defiles, out of which a retreat was difficult. [4] Nor would they have extricated themselves without suffering for their rashness, had not the Macedonians, first, by a shout heard in their rear, and then by an attack begun on that quarter, been utterly dismayed and confounded at the unforeseen danger. [5] Some betook themselves to a hasty flight: some, keeping their stand, rather because they could find no way for flight than that they possessed spirit to support the engagement, were cut off by the Romans, who pressed them hard both on front and rear. [6] Their whole army might have been destroyed, had the victors continued their pursuit of the fugitives; but the cavalry were obstructed by the narrowness of the passes and the ruggedness of the ground; [7] and the infantry, by the weight of their armour. [8] The king at first fled with precipitation, and without looking behind him; but afterwards, when he had proceeded as far as five miles, he began, from recollecting the unevenness of the road, to suspect, (what was really the case,) that the enemy could not follow him; and halting, he despatched his attendants through all the hills and valleys to collect the stragglers together. His loss was not more than two thousand men. [9] The rest of his army, coming to one spot, as if they had followed some signal, marched off, in a compact body, towards Thessaly. The Romans, after having pursued the enemy as far as they could with safety, killing such as they overtook, and despoiling the slain, seized and plundered the king's camp; [10] which, even when it had no defenders, was difficult of access. The following night they were lodged within their own trenches.