Polymnia   

people; a hundred and twenty Orchomenians, from the Arcadian
Orchomenus; and a thousand from other cities: from Corinth, four
hundred men; from Phlius, two hundred; and from Mycenae eighty. Such
was the number from the Peloponnese. There were also present, from
Boeotia, seven hundred Thespians and four hundred Thebans.
Besides these troops, the Locrians of Opus and the Phocians had
obeyed the call of their countrymen, and sent, the former all the
force they had, the latter a thousand men. For envoys had gone from
the Greeks at Thermopylae among the Locrians and Phocians, to call
on them for assistance, and to say- "They were themselves but the
vanguard of the host, sent to precede the main body, which might every
day be expected to follow them. The sea was in good keeping, watched
by the Athenians, the Eginetans, and the rest of the fleet. There
was no cause why they should fear; for after all the invader was not a
god but a man; and there never had been, and never would be, a man who
was not liable to misfortunes from the very day of his birth, and
those misfortunes greater in proportion to his own greatness. The
assailant therefore, being only a mortal, must needs fall from his
glory." Thus urged, the Locrians and the Phocians had come with
their troops to Trachis.
The various nations had each captains of their own under whom they
served; but the one to whom all especially looked up, and who had
the command of the entire force, was the Lacedaemonian, Leonidas.
Now Leonidas was the son of Anaxandridas, who was the son of Leo,
who was the son of Eurycratidas, who was the son of Anaxander, who was
the son of Eurycrates, who was the son of Polydorus, who was the son
of Alcamenes, who was the son of Telecles, who was the son of
Archelaus, who was the son of Agesilaus, who was the son of
Doryssus, who was the son of Labotas, who was the son of
Echestratus, who was the son of Agis, who was the son of
Eurysthenes, who was the son of Aristodemus, who was the son of
Aristomachus, who was the son of Cleodaeus, who was the son of Hyllus,
who was the son of Hercules.
Leonidas had come to be king of Sparta quite unexpectedly.
Having two elder brothers, Cleomenes and Dorieus, he had no
thought of ever mounting the throne. However, when Cleomenes died
without male offspring, as Dorieus was likewise deceased, having
perished in Sicily, the crown fell to Leonidas, who was older than
Cleombrotus, the youngest of the sons of Anaxandridas, and,
moreover, was married to the daughter of Cleomenes. He had now come to
Thermopylae, accompanied by the three hundred men which the law
assigned him, whom he had himself chosen from among the citizens,
and who were all of them fathers with sons living. On his way he had
taken the troops from Thebes, whose number I have already mentioned,
and who were under the command of Leontiades the son of Eurymachus.
The reason why he made a point of taking troops from Thebes, and
Thebes only, was that the Thebans were strongly suspected of being
well inclined to the Medes. Leonidas therefore called on them to
come with him to the war, wishing to see whether they would comply
with his demand, or openly refuse, and disclaim the Greek alliance.
They, however, though their wishes leant the other way, nevertheless
sent the men.
The force with Leonidas was sent forward by the Spartans in
advance of their main body, that the sight of them might encourage the
allies to fight, and hinder them from going over to the Medes, as it
was likely they might have done had they seen that Sparta was
backward. They intended presently, when they had celebrated the
Carneian festival, which was what now kept them at home, to leave a
garrison in Sparta, and hasten in full force to join the army. The
rest of the allies also intended to act similarly; for it happened
that the Olympic festival fell exactly at this same period. None of
them looked to see the contest at Thermopylae decided so speedily;
wherefore they were content to send forward a mere advanced guard.
Such accordingly were the intentions of the allies.