The History Of Herodotus Volume 2 of 2
Page: 187113. Xerxes meanwhile with his army stayed for a few days after the sea-fight, and then they all began to march forth towards Boeotia by the same way by which they had come: for Mardonios thought both that it was well for him to escort the king on his way, and also that it was now too late in the year to carry on the war; it was better, he thought, to winter in Thessaly and then at the beginning of spring to attempt the Peloponnese. When he came to Thessaly, then Mardonios chose out for himself first all those Persians who are called "Immortals," except only their commander Hydarnes (for Hydarnes said that he would not be left behind by the king), and after them of the other Persians those who wore cuirasses, and the body of a thousand horse: also the Medes, Sacans, Bactrians and Indians, foot and horsemen both. 82 These nations he chose in the mass, 83 but from the other allies he selected by few at a time, choosing whose who had fine appearance of those of whom he knew that they had done good service. From the Persians he chose more than from any other single nation, and these wore collars of twisted metal and bracelets; and after them came the Medes, who in fact were not inferior in number to the Persians, but only in bodily strength. The result was that there were thirty myriads in all, including cavalry.
114. During this time, while Mardonios was selecting his army and Xerxes was in Thessaly, there had come an oracle from Delphi to the Lacedemonians, bidding them ask satisfaction from Xerxes for the murder of Leonidas and accept that which should be given by him. The Spartans therefore sent a herald as quickly as possible, who having found the whole army still in Thessaly came into the presence of Xerxes and spoke these words: "O king of the Medes, the Lacedemonians and the sons of Heracles of Sparta demand of thee satisfaction for murder, because thou didst kill their king, fighting in defence of Hellas." He laughed and then kept silence some time, and after that pointing to Mardonios, who happened to be standing by him, he said: "Then Mardonios here shall give them satisfaction, such as is fitting for them to have."
115. The herald accordingly accepted the utterance and departed; and Xerxes leaving Mardonios in Thessaly went on himself in haste to the Hellespont and arrived at the passage where the crossing was in five-and-thirty days, bringing back next to nothing, as one may say, 84 of his army: and whithersoever they came on the march and to whatever nation, they seized the crops of that people and used them for provisions; and if they found no crops, then they took the grass which was growing up from the earth, and stripped off the bark from the trees and plucked down the leaves and devoured them, alike of the cultivated trees and of those growing wild; and they left nothing behind them: thus they did by reason of famine. Then plague too seized upon the army and dysentery, which destroyed them by the way, and some of them also who were sick the king left behind, laying charge upon the cities where at the time he chanced to be in his march, to take care of them and support them: of these he left some in Thessaly, and some at Siris in Paionia, and some in Macedonia. In these parts too he had left behind him the sacred chariot of Zeus, when he was marching against Hellas; but on his return he did not receive it back: for the Paionians had given it to the Thracians, and when Xerxes asked for it again, they said that the mares while at pasture had been carried off by the Thracians of the upper country, who dwelt about the source of the Strymon.