Titus Livius (Livy), The History of Rome, Book 35
Evan T. Sage, PhD professor of latin and head of the department of classics in the University of Pittsburgh, Ed.

29. When day broke the light-armed Cretans and the Tarentine cavalry began the battle on the banks of the river; Telemnastus the Cretan commanded his countrymen, Lycortas of Megalopolis the cavalry; the enemy also employed Cretan auxiliaries and cavalry of the same kind, that is, Tarentini, to protect their water-carriers. [2] For a time the battle was doubtful, since the troops on both sides were of the same character and fought with similar equipment; [3] as the fight went on the tyrant's auxiliaries gained the upper hand, both because they were superior in numbers and because Philopoemen had given his commanders specific instructions that after offering a fairly stiff resistance they should begin to retire and draw the enemy towards the place of the ambuscade. Following the retreating enemy headlong through the defile, many were wounded and slain before they spied the hidden foe. [4] The caetrati had been resting in formation, so far as the width of the valley permitted, so that they easily permitted the fugitives to pass through the intervals in their ranks. [5] Then they themselves arose, unwounded, fresh, in regular array; against an enemy in disorder, scattered, wearied alike by exertions and wounds, they made their charge. [6] Nor was the issue in doubt, and at a rate no little faster than that of their pursuit the soldiers of the tyrant immediately fled and in their rout were driven into their camp. [7] Many were killed and captured in this flight; and there would have been panic in the camp too had not Philopoemen ordered the recall sounded, in fear of the rough [p. 85]and uneven ground where he had heedlessly advanced¹ rather than of the enemy.

[8] Then, drawing inferences both from the outcome of the battle and from the character of the commander what his present fright must be, he sent to him one of the auxiliaries in the guise of a deserter, who reported it as an assured fact that the Achaeans would next [9??] day advance to the Eurotas river, which flowed almost beneath the very walls,² to block the road, that the tyrant might neither have a way to retreat into the city when he wished nor to transport supplies from the city to the [10??] camp, and that the Achaeans might make an effort to find out whether anyone could be influenced towards an inclination to desert the tyrant. The deserter did not so much produce confidence in his words as offer to a man stricken with terror a plausible excuse for abandoning his camp. [11] The next day Nabis ordered Pythagoras with the auxiliaries and the cavalry to stand guard before the rampart; [12] he himself, setting out with the main body of the army, as if to the battlefield, ordered the standards to proceed at quickened pace towards the city.