Titus Livius (Livy), The History of Rome, Book 35
Cyrus Evans, Ed.

30. When Philopœmen saw their army marching precipitately through a narrow and steep road, he sent all his cavalry, together with the Cretan auxiliaries, against the guard of the enemy, stationed in the front of their camp. [2] These, seeing their adversaries approach, and perceiving that their friends had abandoned them, at first attempted to retreat within their works; but afterwards, when the whole force of the Achaeans advanced in order of battle, they were seized with fear, lest, together with the camp itself, they might be taken; [3] they resolved, therefore, to follow the body of their army, which, by this time, had proceeded to a considerable distance in advance. [4] Immediately, the targeteers of the Achaeans assailed and plundered the camp, and the rest set out in pursuit of the enemy. The road was such, that a body of men, even when undisturbed by any fear of a foe, could not, without difficulty, make its way through it. [5] But when an attack was made on their rear, and the shouts of terror, raised by the affrighted troops behind, reached to the van, they threw down their arms, and fled, each for himself, in different directions, into the woods which lay on each side of the road. [6] In an instant of time, the way was stopped up with heaps of weapons, particularly spears, which, falling mostly with their points towards the pursuers, formed a kind of palisade across the road. [7] Philopœmen ordered the auxiliaries to push forward, whenever they could, in pursuit of the enemy, who would find it a difficult matter, the horsemen particularly, to continue their flight; while he himself led away the heavy troops through more open ground to the river Eurotas. [8] There he pitched his camp a little before sun-set, and waited for the light troops which he had sent in chase of the enemy. These arrived at the first watch, and brought intelligence, that Nabis, with a few attendants, had made his way into the city, [p. 1584]and that the rest of his army, unarmed and dispersed, were straggling through all parts of the woods; [9] whereupon, he ordered them to refresh themselves, while he himself chose out a party of men, who, having come earlier into camp, were, by this time, both recruited by food and a little rest; and, ordering them to carry nothing with them but their swords, he marched them out directly, and posted them in the roads which led from two of the gates, one towards Pherae, the other towards the Barbosthenes: for he supposed, that through these the flying enemy would make their retreat. [10] Nor was he mistaken in that opinion; for the Lacedaemonians, as long as any light remained, retreated through the centre of the woods in the most retired paths. As soon as it grew dusk, and they saw lights in the enemy's camp, they kept themselves in paths concealed from view; but having passed it by, they then thought that all was safe, and came down into the open roads, where they were intercepted by the parties lying in wait; [11] and there such numbers of them were killed and taken, that of the whole army scarcely a fourth part effected their escape. [12] As the tyrant was now pent up within the city, Philopœmen employed the greatest part of thirty succeeding days in ravaging the lands of the Lacedaemonians; and then, after greatly reducing, and almost annihilating the strength of the tyrant, he returned home, while the Achaeans extolled him as equal in the glory of his services to the Roman general, and indeed, so far as regarded the war with Lacedaemon, even deemed him superior.