When the Persian came near the pass, the Greeks, alarmed, consulted about a retreat, and it seemed best to the other Peloponnesians to retire to Peloponnesus, and guard the Isthmus; but Leonidas, perceiving the Phocians and Locrians very indignant at this proposition, determined to stay there, and to despatch messengers to the cities, desiring them to come to their assistance, as being too few to repel the army of the Medes. Meantime Xerxes sent a scout on horseback, to see how many they were, and what they were doing. For while he was still in Thessaly, he had heard that a small army had been assembled at that spot, whose leader was Leonidas, of the race of Hercules. When the horseman rode up to the camp, he reconnoitred, and saw not indeed the whole camp, for it was not possible that they should be seen who were posted within the wall, but he had a clear view of those on the outside, whose arms were piled in front of the wall. At this some of the Lacedæmonians were performing gymnastic exercises, and others combing their hair. On beholding this he was astonished, but having ascertained their number, he rode back at his leisure, for no one pursued him, and he met with general contempt. On his return he gave an account to Xerxes of all that he had seen, who could not comprehend the truth, that the Greeks were preparing to be slain and to slay to the utmost of their power.
Xerxes let five days pass, constantly expecting that they would betake themselves to flight. But on the fifth day, as they had not retreated, but appeared to him to stay through arrogance and rashness, in rage he sent the Medes and Cissians against them, with orders to take them alive, and bring them into his presence. When the Medes bore down impetuously upon the Greeks, many of them fell; others followed to the charge, and were not repulsed, though they suffered greatly. But they made it evident to every one, and not least of all to the king himself, that they were indeed many men, but few soldiers. The engagement lasted through the day. The Medes, roughly handled, retired; and the Persians whom the king called "Immortal," and whom Hydarnes commanded, took their place and advanced to the attack, thinking that they indeed should easily settle the business. But they succeeded no better than the Medic troops, but just the same, as they fought in a narrow space, and used shorter spears than the Greeks, and were unable to avail themselves of their numbers. The Lacedæmonians fought memorably, showing that they knew how to fight with men who knew not, and whenever they turned their backs, they retreated in close order; but the barbarians seeing them retreat, followed with a shout and clamor; then they, being overtaken, wheeled round so as to front the barbarians and overthrew an inconceivable number of the Persians; and then some few of the Spartans themselves fell. So that when the Persians were unable to gain any thing in their attempt on the pass, by attacking in troops and in every possible manner, they retired. It is said that during these onsets of the battle, the king, who witnessed them, thrice sprang from his throne, being alarmed for his army. On the following day the barbarians fought with no better success; for considering that the Greeks were few in number, and expecting that they were covered with wounds, and would not be able to raise their heads against them any more, they renewed the contest. But the Greeks were marshalled in companies and according to their several nations, and each fought in turn, except the Phocians, who were stationed at the mountain to guard the pathway. Again the Persians failed and retired.