There were two narrow passes through which Xerxes would have to come before he should find himself in Greece proper, and it was evident that it was at such places as these that the few Greeks could best withstand the numerous Persians. To Tempe, therefore, the northernmost of these passes, a body of troops was hastily despatched, but they soon returned declaring that the defense of the pass was out of the question. All agreed then that the best plan would be to guard Thermopylae, which led from Thessaly into Locris. To-day a swampy plain almost three miles broad lies between Mount Oeta and the Maliac Gulf, but in ancient times there was but a stretch of sand not more than fifty feet wide at its broadest part, and in some places so narrow that a single wagon could scarce pass along it. The Greek fleet was posted off the coast to prevent the Persians from landing men beyond the pass, and a company was at once gathered for the defense of Thermopylae and put under the command of Leonidas, King of Sparta.
"Now, the Greeks that abode the coming of the Persians in this place were these--three hundred Spartans, heavy-armed men; and men of Tegea and Matinea a thousand, from each five hundred, and from Orchomenus one hundred and twenty, and from the rest of Arcadia a thousand. From Corinth there came four hundred, and from Phlius two hundred, and from Mycenae eighty. So many came from the Peloponnesus; of the Boeotians there came seven hundred from Thespiae and four hundred from Thebes. Besides these there had come at the summons the Locrians of Opus with all the men that they had, and a thousand Phocians."
All of the Greeks knew that they were setting out on a dangerous enterprise, but to the Spartans it meant more than that. Leonidas himself felt that he was going to his death, for the oracle at Delphi had foretold that Sparta should be saved if one of her kings should perish, and Leonidas was more than willing to make this sacrifice for his state. His three hundred followers, trained from childhood to look upon death as infinitely preferable to defeat, had, with that courage which has made their name an epithet indicating the highest sort of bravery, celebrated their funeral games before setting out. When they came to the pass of Thermopylae, they found a new cause for fear. This was the path which led over the mountains, and which made possible a descent of the enemy to the rear of those stationed in the pass. However, Leonidas was assured that this mountain track was practically unknown, and that the entrance to it was very difficult to find; so when he had sent a band of Phocians to guard it, he thought little more about it. Many of the soldiers, however, felt that they were being subjected to danger unnecessarily, and insisted that they be allowed to retreat to the Isthmus of Corinth. As this would have guarded only the Peloponnesus and have left the other states at the mercy of the Persians, Leonidas determined that they should remain where they were and await the onset of the enemy.