The Greek Last stand at Thermopylae had perhaps 1400 soldiers
Leonidas was not surprised by the Persians' actions. He was brought up to date on their every action, obtaining news of the Persian outflanking maneuver before first light. Leonidas convened a council before dawn after learning that the Phocians had not held. Some Greeks pushed for evacuation in the face of the overwhelming Persian advance, while others vowed to stay. Following the council, several Greek forces chose to withdraw. Herodotus claimed Leonidas granted their departure with an order, but he also presented an alternative explanation: the retreating army left without orders. 300 Spartans, 700 Thespians, and 400 Thebans were the only soldiers left to guard their retreat. Thus, the Greek last stand at Thermopylae had perhaps 1400 soldiers rather than 300 as stated.
The Spartans had vowed to battle to the death, while the Thebans were being imprisoned against their will. A force of roughly 700 Thespians, led by general Demophilus, the son of Diadromes, refused to leave with the other Greeks and joined the Spartans. The Spartans were ostensibly honoring their promise and the Delphic oracle. It could, however, have been a premeditated strategy to delay the Persian approach and hide the retreat of the Greek army. In truth, with the Persians so close, the decision to stand and the battle was most likely a tactical necessity, one made more appealing by the oracle. The importance of the Thespians' refusal to depart should not be underestimated.
The Greeks sallied forth from the wall this time, hoping to slay as many as they could in the wider part of the pass. They fought with spears until all of them were shattered, then turned to xiphoi (short swords). Abrocomes and Hyperanthes, two of Xerxes' brothers, were killed in this battle, according to Herodotus. Leonidas was also killed in the attack. The Greeks withdrew and took a position on a small hill behind the wall after receiving word that Ephialtes and the Immortals were approaching. The Thebans, led by Leontiades, raised their hands, although a few were slaughtered before the surrender was acknowledged. Some of the last Greeks fought with their hands and teeth. Xerxes surrounded the hill by tearing down a part of the wall, and the Persians poured down arrows until the last Greek was killed.
After losing tens of thousands of men in the first two days of the fight, Xerxes received a lucky break when a Greek named Ephialtes informed him of a mountain route that would carry his army behind the Greek army. With the aim of gaining a prize from the Persians, Ephialtes betrayed his homeland. In the Greek language, his name came to imply "nightmare." Leonidas was aware of the mountain route and had deployed 1,000 Phocians to guard it, but they withdrew wrongly believing that their homeland Phocis was under attack. When Leonidas saw he was being outflanked, he dismissed the majority of the Greek troops.
