The battle of Thermopylae, 480 BC.  

'Of those who perished at the Hot Gates,
all glorious is the fortune, fair the doom;
Their grave's an altar, ceaseless memory's theirs
instead of lamentation, and their fate
Is chant of praise. Such winding sheet as this
no mould nor all-consuming time shall waste.
This sepulchre of valiant men has taken
the fair renown of Hellas for its inmate.
And witness is Leonidas, once king
of Sparta, who hath left behind a crown
Of valour mighty and undying fame'

Darius in 491 had sent envoys to the cities of Greece demanding 'earth and water'. Herodotus says that the Spartans threw them down a well telling them to get earth and water from there. A year later Darius' fleet had been swept away in a storm and his expedition defeated by the Athenians at Marathon. Problems with rebellion in Egypt and over Darius' succession delayed the next expedition. The army that Xerxes his son gathered together in 480 was according to Herodotus the largest ever known.

The Greeks had at first thought to hold the pass of Tempe and a force of 10,000 hoplites was dispatched under Euainetos a Spartan polemarch. This position was quickly abandoned because the position could be turned. Two possible defensive lines remained: the narrow coastal pass of Thermopylae with the fleet in the adjacent north-Euboean strait, or at the Isthmus with the fleet a little to the north at Salamis. Athens was of course in favour of Thermopylae as retreating to the Isthmus meant leaving Athens to the Persian army. The Peloponnesians on the other hand wanted to retreat to the Isthmus in the Peloponnese. Although it has been said that Athenian pressure forced the choice of Thermopylae it could never have been regarded as an all out last ditch effort to stop the Persians. More likely it was regarded by all as a means of gaining time for the preparation of a full army and fleet..

The religious festival of Karneia prevented the full army of Spartans in marching north and so Leonidas set out with 300 picked men who had sons living. By the time he had reached the pass his force consisted of 7,000 hoplites which included 4,000 Peloponnesians, 700 Thespians , 400 Thebans and the full force of Opuntian Locrians and 1,000 Phocians. The Phocians were sent to guard an old track that went around the main position while Leonidas set about building up its defences..

According to Herodotus the Greeks in panic at the size of the Persian army considered withdrawal but at the insistence of the Locrians and Phocians whose territory was most vulnerable they stayed. Xerxes at first sent in envoys to try and persuade the defenders to leave with promises of more and better lands. For three days the Persians delayed, possibly as a result of a storm that pinned the Persian fleet to the coast of Magnesia. On the 4th day the Median and Kissian contingents were ordered forward. The narrowness of the pass meant that the Persians could not fully use their numerical superiority and the skill better weapons and tactics of the Spartans meant the Greeks held the line for two days. Also fighting at close quarters  nullified the Persian advantage in archers On the second day already aware of the path around the Greek positions they found a guide, the path being particularly treacherous especially at night. Thus guided Xerxes sent some of his 10,000 Immortals to turn the Spartan position. What they did not know about were the 1,000 Phocians guarding the path. However these had failed to post pickets and were surprised. Instead of attacking the Persians bypassed them. Once aware that his position had been made untenable Leonidas sent away his Peloponnesian allies and as many of the others as he could and remain with a rear guard. The Thespians Herodotus says volunteered to stay with 80 hoplites from Mycenae and 400 Thebans, Herodotus says that they were compelled but it makes little sense to keep unwilling men and fight a battle at the same time.

The last day saw heavier losses among the Persians than before as the Greeks fought 8 deep at close quarters in particular over the body of Leonidas when he fell. With the arrival of the Persians in the rear the Greeks withdrew into a narrower part of the pass and took up position on a hillock. Here some of the Thebans broke away from the rest and ran towards the Persians to surrender. The final drama was soon over as the Persians fearful to get close used their missiles to deadly effect. 

The results of the battles.

The Persians could now march freely through the pass of Thermopylae and enter Attica. The citizens of Athens had already been evacuated to the nearby island of Salamis when the Persians attacked Athens. The few defenders of Athens were all killed and the city was burnt down to the ground.