The Tegeatans, contesting the post of honour with the Athenians, demanded that, according to custom, the Lacedaemonians being ranged on the right wing of the battle, they might have the left, alleging several matters in commendation of their ancestors. The Athenians being indignant at the claim, Aristides came forward: "To contend with the Tegeatans," said he, "for noble descent and valour, the present time permits not; but this we say to you, O you Spartans, and you the rest of the Greeks, that place neither takes away nor contributes courage; we shall endeavour by crediting and maintaining the post you assign us to reflect no dishonour on our former performances. For we are come, not to differ with our friends, but to fight our enemies; not to extol our ancestors, but ourselves to behave as valiant men. This battle will manifest how much each city, captain, and private soldier is worth to Greece." The council of war, upon this address, decided for the Athenians, and gave them the other wing of the battle.
All Greece being in suspense, and especially the affairs of the Athenians unsettled, certain persons of great families and possessions having been impoverished by the war, and seeing all their authority and reputation in the city vanished with their wealth, and others in possession of their honours and places, convened privately at a house in Plataea, and conspired for the dissolution of the democratic government; and, if the plot should not succeed, to ruin the cause and betray all to the barbarians. These matters being in agitation in the camp, and many persons already corrupted, Aristides, perceiving the design, and dreading the present juncture of time, determined neither to let the business pass unanimadverted upon, nor yet altogether to expose it; not knowing how many the accusation might reach, and willing to set bounds to his justice with a view to the public convenience. Therefore, of many that were concerned, he apprehended eight only, two of whom, who were first proceeded against and most guilty, Aeschines of Lampra and Agesias of Acharnae, made their escape out of the camp. The rest he dismissed;giving opportunity to such as thought themselves concealed to take courage and repent; intimating that they had in the war a great tribunal, where they might clear their guilt by manifesting their sincere and good intentions towards their country.
After this, Mardonius made trial of the Grecian courage, by sending his whole number of horse, in which he thought himself much the stronger, against them, while they were all pitched at the foot of Mount Cithaeron, in strong and rocky places, except the Megarians.
They, being three thousand in number, were encamped on the plain, where they were damaged by the horse charging and making inroads upon them on all hands. They sent, therefore, in haste to Pausanias, demanding relief, as not being able alone to sustain the great numbers of the barbarians. Pausanias, hearing this, and perceiving the tents of the Megarians already hid by the multitude of darts and arrows, and themselves driven together into a narrow space, was at a loss himself how to aid them with his battalion of heavy-armed Lacedaemonians. He proposed it, therefore, as a point of emulation in valour and love of distinction, to the commanders and captains who were around him, if any would voluntarily take upon them the defence and succour of the Megarians. The rest being backward, Aristides undertook the enterprise for the Athenians, and sent Olympiodorus, the most valiant of his inferior officers, with three hundred chosen men and some archers under his command. These being soon in readiness, and running upon the enemy, as soon as Masistius, who commanded the barbarians' horse, a man of wonderful courage and of extraordinary bulk and comeliness of person, perceived it, turning his steed he made towards them. And they sustaining the shock and joining battle with him, there was a sharp conflict, as though by this encounter they were to try the success of the whole war. But after Masistius's horse received a wound and flung him, and he falling could hardly raise himself through the weight of his armour, the Athenians, pressing upon him with blows, could not easily get at his person, armed as he was, his breast, his head, and his limbs all over, with gold and brass and iron; but one of them at last, running him in at the visor of his helmet, slew him; and the rest of the Persians, leaving the body, fled. The greatness of the Greek success was known, not by the multitude of the slain (for an inconsiderable number were killed), but by the sorrow the barbarians expressed. For they shaved themselves, their horses, and mules for the death of Masistius, and filled the plain with howling and lamentation; having lost a person, who, next to Mardonius himself, was by many degrees the chief among them, both for valour and authority.