I’m looking forward to seeing the film, but doesn’t the bravery of 700 Thespians who weren’t professional soldiers but chose to face impossible odds deserve to be remembered?

Herodotus VII.202-3:

These were the Hellenes who awaited the attack of the Persian in this place:–of the Spartans three hundred hoplites; of the men of Tegea and Mantineia a thousand, half from each place, from Orchomenos in Arcadia a hundred and twenty, and from the rest of Arcadia a thousand,–of the Arcadians so many; from Corinth four hundred, from Phlius two hundred, and of the men of Mykene eighty: these were they who came from the Peloponnese; and from the Bœotians seven hundred of the Thespians, and of the Thebans four hundred. In addition to these the Locrians of Opus had been summoned to come in their full force, and of the Phokians a thousand: for the Hellenes had of themselves sent a summons to them, saying by messengers that they had come as forerunners of the others, that the rest of the allies were to be expected every day, that their sea was safely guarded, being watched by the Athenians and the Eginetans and by those who had been appointed to serve in the fleet, and that they need fear nothing: for he was not a god, they said, who was coming to attack Hellas, but a man; and there was no mortal, nor would be any, with those fortunes evil had not been mingled at his very birth, and the greatest evils for the greatest men; therefore he also who was marching against them, being mortal, would be destined to fail of his expectation. They accordingly, hearing this, came to the assistance of the others at Trachis.

Leonidas takes the omens and dismisses the allies. Then…

Herodotus VII.222-7

The allies then who were dismissed departed and went away, obeying the word of Leonidas, and only the Thespians and the Thebans remained behind with the Lacedemonians. Of these the Thebans stayed against their will and not because they desired it, for Leonidas kept them, counting them as hostages; but the Thespians very willingly, for they said that they would not depart and leave Leonidas and those with him, but they stayed behind and died with them. The commander of these was Demophilos the son of Diadromes.

Xerxes meanwhile, having made libations at sunrise, stayed for some time, until about the hour when the market fills, and then made an advance upon them; for thus it had been enjoined by Epialtes, seeing that the descent of the mountain is shorter and the space to be passed over much less than the going round and the ascent. The Barbarians accordingly with Xerxes were advancing to the attack; and the Hellenes with Leonidas, feeling that they were going forth to death, now advanced out much further than at first into the broader part of the defile; for when the fence of the wall was being guarded, they on the former days fought retiring before the enemy into the narrow part of the pass; but now they engaged with them outside the narrows, and very many of the Barbarians fell: for behind them the leaders of the divisions with scourges in their hands were striking each man, ever urging them on to the front. Many of them then were driven into the sea and perished, and many more still were trodden down while yet alive by one another, and there was no reckoning of the number that perished: for knowing the death which was about to come upon them by reason of those who were going round the mountain, they displayed upon the Barbarians all the strength which they had, to its greatest extent, disregarding danger and acting as if possessed by a spirit of recklessness.

Now by this time the spears of the greater number of them were broken, so it chanced, in this combat, and they were slaying the Persians with their swords; and in this fighting fell Leonidas, having proved himself a very good man, and others also of the Spartans with him, men of note, of whose names I was informed as of men who had proved themselves worthy, and indeed I was told also the names of all the three hundred. Moreover of the Persians there fell here, besides many others of note, especially two sons of Dareios, Abrocomes and Hyperanthes, born to Dareios of Phratagune the daughter of Artanes: now Artanes was the brother of king Dareios and the son of Hystaspes, the son of Arsames; and he in giving his daughter in marriage to Dareios gave also with her all his substance, because she was his only child. Two brothers of Xerxes, I say, fell here fighting; and meanwhile over the body of Leonidas there arose a great struggle between the Persians and the Lacedemonians, until the Hellenes by valour dragged this away from the enemy and turned their opponents to flight four times.

This conflict continued until those who had gone with Epialtes came up; and when the Hellenes learnt that these had come, from that moment the nature of the combat was changed; for they retired backwards to the narrow part of the way, and having passed by the wall they went and placed themselves upon the hillock, all in a body together except only the Thebans: now this hillock is in the entrance, where now the stone lion is placed for Leonidas. On this spot while defending themselves with daggers, that is those who still had them left, and also with hands and with teeth, they were overwhelmed by the missiles of the Barbarians, some of these having followed directly after them and destroyed the fence of the wall, while others had come round and stood about them on all sides.

Such were the proofs of valour given by the Lacedemonians and Thespians; yet the Spartan Dienekes is said to have proved himself the best man of all, the same who, as they report, uttered this saying before they engaged battle with the Medes:–being informed by one of the men of Trachis that when the Barbarians discharged their arrows they obscured the light of the sun by the multitude of the arrows, so great was the number of their host, he was not dismayed by this, but making small account of the number of the Medes, he said that their guest from Trachis brought them very good news, for if the Medes obscured the light of the sun, the battle against them would be in the shade and not in the sun. This and other sayings of this kind they report that Dienekes the Lacedemonian left as memorials of himself; and after him the bravest they say of the Lacedemonians were two brothers Alpheos and Maron, sons of Orsiphantos. Of the Thespians the man who gained most honour was named Dithyrambos son of Harmatides.