When the marshalling of Mardonius' troops by nations and by maniples was ended, the two armies proceeded on the next day to offer sacrifice. The Grecian sacrifice was offered by Tisamenus, the son of Antiochus, who accompanied the army as soothsayer: he was an Elean, and belonged to the Clytiad branch of the Iamidae, but had been admitted among their own citizens by the Lacedaemonians. Now his admission among them was on this wise:- Tisamenus had gone to Delphi to consult the god concerning his lack of offspring, when it was declared to him by the Pythoness that he would win five very glorious combats. Misunderstanding the oracle, and imagining that he was to win combats in the games, Tisamenus at once applied himself to the practice of gymnastics. He trained himself for the Pentathlum, and, on contending at Olympia, came within a little of winning it; for he was successful in everything, except the wrestling-match, which was carried off by Hieronymus the Andrian.

Hereon the Lacedaemonians perceived that the combats of which the oracle spoke were not combats in the games, but battles: they therefore sought to induce Tisamenus to hire out his services to them, in order that they might join him with their Heracleid kings in the conduct of their wars. He however, when he saw that they set great store by his friendship, forthwith raised his price, and told them, "If they would receive him among their citizens, and give him equal rights with the rest, he was willing to do as they desired, but on no other terms would they ever gain his consent." The Spartans, when they heard this, at first thought it monstrous, and ceased to implore his aid. Afterwards, however, when the fearful danger of the Persian war hung over their heads, they sent for him and agreed to his terms; but Tisamenus now, perceiving them so changed, declared, "He could no longer be content with what he had asked before: they must likewise make his brother Hagias a Spartan, with the same rights as himself."In acting thus he did but follow the example once set by Melampus, at least if kingship may be compared with citizenship. For when the women of Argos were seized with madness, and the Argives would have hired Melampus to come from Pylos and heal them of their disease, he demanded as his reward one-half of the kingdom; but as the Argives disdained to stoop to this, they left him and went their way.

Afterwards, however, when many more of their women were seized, they brought themselves to agree to his terms; and accordingly they went again to him, and said they were content to give what he required.

Hereon Melampus, seeing them so changed, raised his demand, and told them, "Except they would give his brother Bias one-third of the kingdom likewise, he would not do as they wished." So, as the Argives were in a strait, they consented even to this.

In like manner the Spartans, as they were in great need of Tisamenus, yielded everything: and Tisamenus the Elean, having in this way become a Spartan citizen, afterwards, in the capacity of soothsayer, helped the Spartans to gain five very glorious combats. He and his brother were the only men whom the Spartans ever admitted to citizenship. The five combats were these following:- The first was the combat at Plataea; the second, that near Tegea, against the Tegeans and the Argives; the third, that at Dipaeeis, against all the Arcadians excepting those of Mantinea; the fourth, that at the Isthmus, against the Messenians; and the fifth, that at Tanagra, against the Athenians and the Argives. The battle here fought was the last of all the five.

The Spartans had now brought Tisamenus with them to the Plataean territory, where he acted as soothsayer for the Greeks. He found the victims favourable, if the Greeks stood on the defensive, but not if they began the battle or crossed the river Asopus.