The cause of Hyperbolus's banishment is said to have been this. Alcibiades and Nicias, men that bore the greatest sway in the city, were of different factions. As the people, therefore, were about to vote the ostracism, and obviously to decree it against one of them, consulting together and uniting their parties, they contrived the banishment of Hyperbolus. Upon which the people, being offended, as if some contempt or affront was put upon the thing, left off and quite abolished it. It was performed, to be short, in this manner. Every one taking an ostracon, that is, a sherd, a piece of earthenware, wrote upon it the citizen's he would have banished, and carried it to a certain part of the market-place surrounded with wooden rails. First, the magistrates numbered all the sherds in gross (for if there were less than six thousand, the ostracism was imperfect); then, laying every name by itself, they pronounced him whose name was written by the largest number, banished for ten years, with the enjoyment of his estate. As, therefore, they were writing the names on the sherds, it is reported that an illiterate clownish fellow, giving Aristides his sherd, supposing him a common citizen, begged him write Aristides upon it; and he being surprised and asking if Aristides had ever done him any injury, "None at all," said he, "neither know I the man; but I am tired of hearing him everywhere called the Just." Aristides, hearing this, is said to have made no reply, but returned the sherd with his own name inscribed. At his departure from the city, lifting up his hands to heaven, he made a prayer (the reverse, it would seem, of that of Achilles), that the Athenians might never have any occasion which should constrain them to remember Aristides.

But three years afterwards, when Xerxes was marching through Thessaly and Boeotia into the country of Attica, they repealed the law, and decreed the return of the banished: chiefly fearing lest Aristides might join himself to the enemy, and bring over many of his fellow-citizens to the party of the barbarians; much mistaking the man, who, already before the decree, was exerting himself to excite and encourage the Greeks to the defense of their liberty.

After the battle of Salamis, Xerxes, much terrified, immediately hastened to the Hellespont. But Mardonius was left with the most serviceable part of the army, about three hundred thousand men, and was a formidable enemy, confident in his infantry, and writing messages of defiance to the Greeks: "You have overcome by sea men accustomed to fight on land and unskilled at the oar; but there lies now the open country of Thessaly; and the plains of Boeotia offer a broad and worthy field for brave men, either horse or foot, to contend in."

But he sent privately to the Athenians, both by letter and word of mouth from the king, promising to rebuild their city, to give them a vast sum of money, and constitute them lords of all Greece on condition they would not engage in the war. The Lacedaemonians receiving news of this, and fearing, dispatched an embassy to the Athenians, entreating that they would send their wives and children to Sparta, and receive support from them for their superannuated. For, being despoiled both of their city and country, the people were suffering extreme distress. Having given audience to the ambassadors, they returned an answer, upon the motion of Aristides, worthy of the highest admiration; declaring, that they forgave their enemies if they thought all things purchasable by wealth, than which they knew nothing of greater value; but that they felt offended at the Lacaemonians, for looking only to their present poverty, without any remembrance of their valor and magnanimity, and offering them their victuals, to fight in the cause of Greece. Aristides made this proposal, brought back the ambassadors into the assembly, and charged them to tell the Lacaemonians that all the treasure on earth or under it was of less value with the people of Athens than the liberty of Greece. And, showing the sun to those who came from Mardonius, "as long as that retains the same course, so long," said he, "shall the citizens of Athens wage war with the Persians for the country which has been wasted, and the temples that have been profaned and burnt by them." Moreover, he proposed a decree, that the priests should anathematize him who sent any herald to the Medes, or deserted the alliance of Greece.

When Mardonius made a second incursion into the country of Attica, the people passed over again into the isle of Salamis. Aristides himself went to Lacedaemon, and reproved them for the delay and neglect in abandoning Athens once more to the barbarians; and demanded their assistance for that part of Greece which was not yet lost. The Ephori, hearing this, made show of sporting all day, and of carelessly keeping holy day (for they were then celebrating the Hyacinthian festival), but in the night, selecting five thousand Spartans, each of whom was attended by seven Helots, they sent them forth unknown to those from Athens. And when Aristides again reprehended them, they told him in derision that he either doted or dreamed, for the army was already at Oresteum, in their march towards the strangers; as they called the Persians. Aristides answered that they jested unreasonably, deluding their friends, instead of their enemies.

Being chosen general for the war, he repaired to Plataea, with eight thousand Athenians, where Pausanias, generalissimo of all Greece, joined him with the Spartans; and the forces of the other Greeks came in to them. The encampment of the barbarians extended all along the bank of the river Asopus, their numbers being so great, there was no enclosing them all, but their baggage and most valuable things were surrounded with a square bulwark, each side of which was the length of ten furlongs.

The Tegeatans, contesting the post of honor 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 and said: "To contend with the Tegeatans for noble descent and valor, 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 endeavor by maintaining the post you assign us, to reflect no dishonor 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 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.

At this juncture, 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, except the Megarians, encamped at the foot of Mount Cithaeron, in strong and rocky places. They being three thousand in number, had pitched their tents on the plain, where the cavalry charged and made inroads upon them from all sides. They sent, therefore, in haste to Pausanias, demanding relief, not being able alone to sustain the great numbers of the barbarians. Pausanias, hearing this, and perceiving the tents of the Megarians almost hidden by the multitude of darts and arrows, and themselves driven together into a narrow space, was at a loss how to aid them with his battalions of heavy-armed Lacedaemonians. He asked, therefore, as a test of emulation and love of distinction, to the commanders and captains who were around him, if any would voluntarily take upon the defense and succor 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 were soon in readiness, and running upon the enemy, as soon as it was perceived by Masistius, who commanded the cavalry of the barbarians, a man of wonderful courage and of extraordinary bulk and comeliness of person, he turned his steed and made towards them. They sustained the shock and joined battle with him, 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 armor, the Athenians pressed upon him with blows, but could not easily get at his person, armed as he was, breast, head, and limbs all over, with gold and brass and iron; but one of them at last, running a javelin under 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 far the chief among them, both for valor and authority.

After this skirmish of the horse, they kept from fighting a long time; for the soothsayers, by the sacrifices, foretold the victory both to Greeks and Persians, if they stood upon the defensive part only, but if they became aggressors, the contrary. At length Mardonious, when he had but a few days' provision, and the Greek forces were increasing continually, impatient of delay, determined to lie still no longer, but passing Asopus by daybreak, to fall unexpectedly upon the Greeks. This he signified the night before to the captains of his host. But about midnight, a certain horseman stole into the Greek camp, and coming to the watch, desired them to summon Aristides, the Athenian, to him. He came speedily, and the stranger said: "I am Alexander, king of the Macedonians, and have come here through the greatest danger in the world for the goodwill I bear you, lest a sudden onset should dismay you, so as to behave in the fight worse than usual. For to-morrow Mardonius will give you battle, urged, not by any hope of success or courage, but by want of victuals: for the prophets prohibit him from the battle, the sacrifices and oracles being unfavorable; but the army is in despondency and consternation; and necessity forces him to try his fortune, or sit still and endure the last extremity of want." Alexander, thus saying, entreated Aristides to take notice and remember him, but not tell any other. But he replied that it was not fair conceal to the matter from Pausanias (because he was general); as for any others he would keep it secret from them till the battle was fought; but if the Greeks obtained the victory, that then no one should be ignorant of Alexander's goodwill and kindness towards them. After this, the king of the Macedonians rode back again, and Aristides went to Pausanias's tent and told him; and they sent for the rest of the captains and gave orders that the army should be in battle array.