It was midsummer in the year 480 B.C. when the Persian host left Therma and marched down through Thessaly to the Pass of Thermopylae. The Persians encamped before the Pass and a scout was sent forward to bring back information as to what the Greeks were doing. Only a small force of Greeks was defending the Pass, the main part of the Greek army was kept back further to the south to defend the Isthmus. A small body of about three hundred Spartans had been sent under their King Leonidas to defend the Pass of Thermopylae, and, if possible, to prevent the Persians from advancing further into Greece. These three hundred men were the picked body-guard of the King, a force in which only fathers of sons might serve, so that their families might not die out of Sparta.
The Persian scout went cautiously forward, and to his great surprise saw some of the Spartans practising athletic exercises and others combing their long hair. He could not see the rest, as an ancient wall built across the Pass hid them from sight. He returned to Xerxes and reported on what he had seen. The King sent for a Greek who was in his camp and asked him what this behaviour of the Spartans might mean. He told him that they were following an ancient Spartan custom, for "whenever they are about to put their lives in peril, then they attend to the arrangement of their hair." The Spartans knew against what odds they had to fight, but their duty had placed them where they were, and no Spartan ever retreated or turned his back upon his foe.
The Great King intended to attack at the same moment both by land and by sea. The fleets were at Artemisium, and there were four times as many Persian ships as Greek. A hot and sultry summer's day had passed, and the signal to attack was expected in the morning. But at early dawn the sea began to be violently agitated and a strong east wind arose, thunder rumbled in the distance, and soon a terrible storm broke. The Greek ships were in safety, but a large number of Persian ships were wrecked and great treasure was lost. For three days the storm continued, and for three days Xerxes had to wait before he could attack the Pass. When on the fourth day the storm died down, the sea fight began. Three times over the Greeks attacked the Persian ships, and each time they prevailed against them. After the third fight, news was brought to Themistocles, the Athenian admiral, that two hundred Persian ships, sailing to the Greek rear, had been lost in the storm, so that there was nothing more to fear from an attack in that direction. The Greeks succeeded in throwing the Persian ships into confusion and so crippled the fleet, that they finally won the battle. It was then that Xerxes gave the order to his army to attack the Pass.
For the whole of a hot summer's day the Persians attacked. First the Medes tried to force the Pass, but it was narrow, and as they met the Spartan spears, down they went, man after man. Hour after hour this continued, but every attack was repulsed and hardly a Spartan fell. Then the Medes withdrew and the Immortals took their place. They were fresh and greatly superior to the Spartans in numbers, but neither could they prevail against them. At times the Spartans would make a pretence of turning to flight, but when the Barbarians followed after them with shouting and clashing of arms, then they turned and faced the Barbarians and slew large numbers of them. The Spartans lost a few men, but at the end of the day the Persians drew back, exhausted and defeated, and the Spartans still held the Pass.
The next day, the same thing happened. So great was the slaughter of the Persians on this day that three times Xerxes leapt up from the seat from which he was watching the fight, in deadly fear for his army. But by the end of the day the Pass had not been taken, and again the Persians withdrew, exhausted and driven back, leaving large numbers of their companions lying dead before the Pass.
Xerxes was in great straits as to what he should do next, when he was told that a man desired audience of him. He was a Greek who lived in that region, and he offered, if the Persian would reward him with enough gold, to lead his army by a path known to him, but of which the Spartans were ignorant, over the mountain to a spot from which the Pass might be attacked in the rear. It was a long and difficult path, but the traitor knew it well and would guide them surely. The reward was promised, and about the time when the lamps were lit in the camp, the Immortals with their commander set out under the guidance of the traitor. All through the long black night they climbed by a steep and rocky path, and when dawn appeared they had reached the summit of the mountain. In this region a thousand men of Phocis were stationed to protect their own country and the path which led down to the valley below. They could not see the Persians as they climbed, for the sides of the mountain were covered with oak trees, but in the great silence which falls upon nature just before the dawn, suddenly these men heard an unexpected sound. It was the Persians stepping on the dried oak leaves which lay thickly on the ground beneath their feet. The Greeks started up and when the Persians, coming suddenly upon them, discharged their arrows at them, they retreated to a higher position close at hand, where they waited for the expected attack. To their surprise, however, the enemy turned away and left them. On went the traitor followed by the Persians, until they were on the road in the rear of Leonidas.
While it was yet night, scouts came down from the mountains where they had been keeping watch, and told Leonidas that the Pass was turned, and that the enemy was approaching it from the rear. Leonidas knew what that meant, the end had come, but he commanded Spartans and he knew that whilst one remained alive, the Pass would not be taken.
At sunrise, according to the arrangement made with the traitor, Xerxes attacked. The Spartans, knowing that they were going forth to death, now advanced further out into the broader space in front of the Pass, where there was more room. And then followed a fight which will never be forgotten. The Barbarians made attack after attack, and the Spartans slew them and drove them back every time. Many were driven into the sea and perished, and many more were trodden down while still alive and trampled to death, and there was no reckoning of the number that perished. Two brothers of Xerxes fell fighting, and then Leonidas fell. The Spartans fought for the body of their King; most of their spears were by this time broken, so they fought and slew the Persians with their swords. Four times the Persians had almost taken the body of the King, and four times they were driven back by the Spartans, when word came that the Immortals were attacking the Pass in the rear. Then the remaining Spartans placed themselves with the body of Leonidas behind the wall, and there they made their last defence. On this spot those who still had them defended themselves with daggers, and those who had no weapons left, fought with their hands and teeth, until, overwhelmed by the Barbarians who were now assailing them both in the front and in the rear, they were surrounded and cut down, until not a Spartan was left alive.
And so the Persians took the Pass, and the road to Athens lay clear before them.