Pausanias was in despair when the water supply was stopped, and he determined to withdraw and take up a position nearer to Plataea, where both food and water would be secure.
Discipline had grown slack in the Greek camp, and the retreat, which began at night, was carried out in a disorderly manner.
One company set off in haste, but did not halt where Pausanias had arranged that it should. The Spartans refused to move at all. One of their captains, ‘lifting a piece of rock with both hands and flinging it at the feet of Pausanias, cried, “Thus do I cast my vote against the counsel of flying from the strangers.”’ Only when the retreat was nearly ended did the Spartans tardily obey the order to withdraw. This was how it happened that, when morning dawned, the Persians found that the enemy had disappeared, all but the Spartans, whose captain had delayed to follow the orders of Pausanias.
When Mardonius caught sight of the loiterers he ordered his men to set out in pursuit of them, and before the Spartans could get into position the Persians were upon them. But Pausanias soon learned what was taking place in his rear, and he hastened back with the troops that were with him to aid the disobedient Spartans.
The Persians had thrust their shields into the ground to form a rough barrier between them and the Spartans, while they sent shower after shower of arrows upon the loiterers. The Spartans soon tore down the breastwork of shields, and with their swords in their hands advanced upon the enemy.
Mardonius did all he could to encourage his men, but they had no armour to protect them from the blows of the Spartans, and they were forced back toward the river, throwing into confusion those of their own army who were still advancing.
In the thick of the battle Mardonius rode on a white horse, surrounded by ten thousand chosen Persians. He was easily known by his white charger, and many were the spears that were aimed at him by the angry Spartans. At length one smote him so that he fell dead to the ground. ‘Thus,’ says Herodotus, ‘Mardonius paid the recompence for the murder of Leonidas.’
No sooner was their leader slain than the Persians fled in utter confusion, all but forty thousand who were led off the field by one of the generals, and these marching north reached the Hellespont and crossed over to Asia in safety.
Those who fled from the field took refuge in their camp, where the Spartans attacked them. But the barricades were strong, and the camp was not taken until the Athenians had returned and joined in the assault.
As the Greeks swarmed into the camp they slaughtered the enemy without mercy. So severe was the defeat of Plataea that the Persians were utterly crushed.