Polymnia   

Hydarnes, whom the king called his "Immortals": they, it was
thought, would soon finish the business. But when they joined battle
with the Greeks, 'twas with no better success than the Median
detachment- things went much as before- the two armies fighting in a
narrow space, and the barbarians using shorter spears than the Greeks,
and having no advantage from their numbers. The Lacedaemonians
fought in a way worthy of note, and showed themselves far more skilful
in fight than their adversaries, often turning their backs, and making
as though they were all flying away, on which the barbarians would
rush after them with much noise and shouting, when the Spartans at
their approach would wheel round and face their pursuers, in this
way destroying vast numbers of the enemy. Some Spartans likewise
fell in these encounters, but only a very few. At last the Persians,
finding that all their efforts to gain the pass availed nothing, and
that, whether they attacked by divisions or in any other way, it was
to no purpose, withdrew to their own quarters.
During these assaults, it is said that Xerxes, who was watching
the battle, thrice leaped from the throne on which he sate, in
terror for his army.
Next day the combat was renewed, but with no better success on the
part of the barbarians. The Greeks were so few that the barbarians
hoped to find them disabled, by reason of their wounds, from
offering any further resistance; and so they once more attacked
them. But the Greeks were drawn up in detachments according to their
cities, and bore the brunt of the battle in turns- all except the
Phocians, who had been stationed on the mountain to guard the pathway.
So, when the Persians found no difference between that day and the
preceding, they again retired to their quarters.
Now, as the king was in great strait, and knew not how he should
deal with the emergency, Ephialtes, the son of Eurydemus, a man of
Malis, came to him and was admitted to a conference. Stirred by the
hope of receiving a rich reward at the king's hands, he had come to
tell him of the pathway which led across the mountain to
Thermopylae; by which disclosure he brought destruction on the band of
Greeks who had there withstood the barbarians. This Ephialtes
afterwards, from fear of the Lacedaemonians, fled into Thessaly; and
during his exile, in an assembly of the Amphictyons held at Pylae, a
price was set upon his head by the Pylagorae. When some time had
gone by, he returned from exile, and went to Anticyra, where he was
slain by Athenades, a native of Trachis. Athenades did not slay him
for his treachery, but for another reason, which I shall mention in
a later part of my history: yet still the Lacedaemonians honoured
him none the less. Thus then did Ephialtes perish a long time
afterwards.
Besides this there is another story told, which I do not at all
believe- to wit, that Onetas the son of Phanagoras, a native of
Carystus, and Corydallus, a man of Anticyra, were the persons who
spoke on this matter to the king, and took the Persians across the
mountain. One may guess which story is true, from the fact that the
deputies of the Greeks, the Pylagorae, who must have had the best
means of ascertaining the truth, did not offer the reward for the
heads of Onetas and Corydallus, but for that of Ephialtes of
Trachis; and again from the flight of Ephialtes, which we know to have
been on this account. Onetas, I allow, although he was not a Malian,
might have been acquainted with the path, if he had lived much in that
part of the country; but as Ephialtes was the person who actually
led the Persians round the mountain by the pathway, I leave his name
on record as that of the man who did the deed.
Great was the joy of Xerxes on this occasion; and as he approved
highly of the enterprise which Ephialtes undertook to accomplish, he
forthwith sent upon the errand Hydarnes, and the Persians under him.
The troops left the camp about the time of the lighting of the
lamps. The pathway along which they went was first discovered by the
Malians of these parts, who soon afterwards led the Thessalians by