History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
And they would have suffered more than any part of the whole army if their cavalry had not been present and proved helpful to them. It happened, too, that Agis, perceiving that the left of his own forces, which was opposed to the Mantineans and the thousand Argives, was in distress, gave orders for the whole army to go to the assistance of the part that was in danger of defeat.
When this was done, the Athenians, as the enemy's force passed on and moved away from them, quietly made their escape, and with them the part of the Argives that had been worsted. The Mantineans and their allies, on the other hand, and the picked men of the Argives, were no longer disposed to press home the attack on their opponents, but seeing their own side defeated and the Lacedaemonians bearing down upon them, turned to flight.
On the part of the Mantineans the losses were more serious, but of the picked men of the Argives the greater part was saved. The flight, however, was not hotly pursued, nor did the retreat extend to any great distance; for the Lacedaemonians fight their battles long and stubbornly, standing their ground until they rout their foes, but when they have routed them their pursuits are brief and only for a little distance.
Such, then, was the battle—or as like as possible to this description—being the greatest that had occurred within a very long time between Hellenic forces, and fought by the most famous states.
The Lacedaemonians, halting in front of their enemies' dead, straightway set up a trophy and stripped the slain, then took up their own dead and withdrew to Tegea, where they buried them, giving up under truce those of the enemy.
There were slain, of the Argives, Orneates and Cleonaeans seven hundred, of the Mantineans two hundred, of the Athenians, together with the Aeginetans,[*](Athenian colonists settled in Aegina; cf. 2.27.1.) two hundred, and both their generals. On the side of the Lacedaemonians, the allies did not suffer so that any number worth mentioning was missing; about themselves it was difficult to learn the truth, but near three hundred were said to have been killed.