The battle of Thermopylae (August 480 BC) is one of the most famous military defeats in history, and is best known for the fate of the 300 Spartans, killed alongside 700 Thespians on the final day of the battle (Greco-Persian Wars).
In 490 the Persian Emperor Darius had sent an invasion force across the Aegean to punish Eretria and Athens for their support of the Ionian Revolt. This force had been defeated at the Battle of Marathon, and Darius had died before he could launch a second invasion. His successor, Xerxes, first had to deal with a revolt in Egypt, but he then began massive preparations for his own invasion of Greece. This time the Emperor planned to lead the army in person. Several years of work went into the expedition, before Xerxes set off from Sardis in Lydia in the spring of 480 BC.
Many Greek states, especially in the north of the country, decided to submit to the Persians, but further south most decided to resist, led by Athens and Sparta. The Greek allies met at the Isthmus of Corinth to decide what to do. The initial plan was to hold the Vale of Tempe, on the border between Macedonia and Thessaly, but this position was too easy to outflank - there was an inland route into Thessaly from Macedonia, and that was the one chosen by Xerxes. A force was sent forward to Tempe, but then pulled back to the Isthmus of Corinth and tried to decide what to do next.
Their decision was to defend the narrow pass of Thermopylae, while the fleet was posted at Artemisium on the coast of Euboea. This would prevent the Persians fleet from outflanking the Greeks without sailing all the way around Euboea, a trip that would have left the army without naval support.
The land forces were commanded by King Leonidas of Sparta, although his country famously only provided 300 men. Herodotus gives a detailed breakdown of the Greek forces, which appears to be rather more realistic than his report of the Persian forces. The largest contingent of heavy infantry came from the Peloponnese. As well as the 300 Spartiates (not including Leonidas), there were 500 from Tegea, 500 from Mantinea, 120 from Orchomenus in Arcadia, 1,000 from the rest of Arcadia, 400 from Corinth, 200 from Phleious and 80 from Mycenae, a total of 3,100. Boeotia provided 700 from Thespiae and 400 from Thebes (despite that city having decided to side with the Persians). The Opuntian Locrians sent every available man (not a very helpful statement on Herodotus's part) and Phocia sent 1,000. This gives us 5,200 and the Locrians, a total of around 7,000 hoplites and an unstated number of lighter troops. Leonidas had deliberately recruited the Thebans in an attempt to discover where their loyalty laid.
The rest of the Spartan army was waiting for the end of the festival of Carnea before they could march. They have often been blamed for this attitude, but most of the other contingents were also only advance guards, as the Persian invasion coincided with the Olympic festival and the Greeks expected the Persians to be held up at Thermopylae for some time.
The pass of Thermopylae no longer exists. In antiquity it was a narrow strip of land with the sea on one side and cliffs towering above it on the other. Since then the shallow sea has silted up, and a mile-wide plain now sits between the cliffs and the water.
Herodotus provides us with an estimate of the size of the Persian army. He gives Xerxes 1,700,000 infantry and 80,000 cavalry from Asia and another 300,000 from Europe, for a total of just over two million fighting men. The core of the army was made up by the much smaller contingents from Persia, Media and the Sacae, a Scythian tribe. Adding in the naval forces and non-combatants he comes up with a grand total of 5,283,220 men. This figure had been discounted as just about impossible by just about everyone who has examined it. Herodotus's 1.7 million was supported by a list of nearly fifty contingents that made up the Persian army and perhaps represents a theoretical maximum if every one of these forces was raised in full - it would come out at just over 30,000 each, far less unconvincing. The big problem with Herodotus's vast force is that it would have been logistically impossible to support. The general consensus now is that Xerxes had around 200,000 men, but given a lack of reliable way to calculate the size of his army that can only be a guess.
Xerxes waited for four days after arriving at the northern end of the pass, possibly because he expected the Greeks to retreat, or possibly because he wanted to coordinate the land attack with an expected naval battle.
On the first day of the battle Xerxes launched a costly frontal assault on the Greek position, defended by most of the 7,000 Greeks. This attack was easily repulsed. The first attack was made by the Medes and Cissians. They found that narrow pass negated their numbers, and their shorter spears made it difficult for them to come to grips with the Greeks. In addition their weight of numbers made it difficult for the Medes and Cissians to withdraw, and they suffered heavy losses in a long battle. Eventually they were able to withdraw and Xerxes then sent in his Immortals, the best 10,000 men in the Persian contingent. The Immortals were also unable to make any progress. The Spartans made a number of feigned retreats, tricking the Persians into an undisciplined pursuit before turning back and cutting into them.
This pattern was repeated on the second day of the battle. This time the Phocians were sent to guard a path through the mountains inland of the coastal pass, while the other Greek contingents fought in turn in the pass. Once again the Persians were forced to pull back at the end of the day.
That night a Greek, Ephialtes, offered to guide the Persians along mountain paths that led behind the Greek position. Xerxes sent Hydarnes and a contingent of troops along the path, starting at dusk on the second day of the battle. At the top of the pass they found the thousand Phocians who had been sent to guard the path. When the Persians attacked them the Phocians retreated to a nearby mountain top and prepared to fight to the death, but instead they had to watch as the Persian force ignored them and continued on down the path.
Just before dawn on the third day some deserters warned the Greeks that the Persians were on the mountain path. A short time later the Greek scouts arrived, reporting the same thing. Naturally this caused a drop in Greek morale, and many of the contingents began to prepare to leave. Leonidas is said to have recognised this and ordered most of the other contingents to go. Only three contingents stayed - the survivors of the 300 Spartans, 700 Thespians and 400 Thebans. The Thebans were probably kept almost as hostages, but the Thespians were fighting to defend their homeland, which would be first to fall to the Persians. The final battle of 'The 300' was thus the stand of the 1,300, minus any casualties from the first two days of the battle and plus any light troops and helots unrecorded by Herodotus.
On the third day the Greeks advanced out of the narrowest part of the pass and fought in a wider area. They were able to inflict very heavy casualties on the Persians attacking from the front, but eventually Leonidas was killed. His men rescued his body and even pushed the Persians back four times. During the battle two of Xerxes' sons were killed, Abrocomes and Hyperanthes. In a typically tangled family tree their mother Phratagoune was the daughter of Artanes, a half-brother of Darius.
Greek resistance was finally broken after the Persians sent across the mountain paths arrived in their rear. The surviving Spartans and Thespians pulled back to the narrowest part of the pass, where they made a grim last stand where a wall blocked the pass. By now most had lost their spears and were described as fighting with daggers, or hands and teeth.
Only two of the Spartiates survived the battle. Aristodamus was either recovering from an eye injury or serving as a messenger, and chose not to return to the army. He returned to Sparta where he was disgraced, but in the following year he redeemed himself at Plataea. The second, Pantites, was carrying a message to Thessaly. Despite having a legitimate reason to be away from the battle he was also disgraced at Sparta and committed suicide.
The Thebans fought with the Greeks during the first two days of the battle and during the first phase of the third day, but when the Spartans and Thespians withdrew to the wall they took their chance to surrender.
The Greek fleet, which had been holding its own at Artemisium, also retreated south, taking up a new position in the straits of Salamis.
Three monuments were erected at Thermopylae soon after the battle, none of which were fair to the Thespians. One recorded that
Here once were three million of the foe
Opposed by four thousand from the Peloponnese
The second, and most famous, read
Stranger, tell the people of Lacedaemon
That we who lie here obeyed their commands
The third was to the diviner Megistias, who chose to fight on the third day and was killed in the battle.
According to Herodotus the Persians lost 20,000 dead at Thermopylae. The Greek losses are uncertain. According to Herodotus Xerxes was later able to display 4,000 Greek bodies at Thermopylae, which included the Thespian and Spartiate dead from the third day of the battle, any casualties from the first two days, and the helots killed alongside their Spartan masters.
In the aftermath of Thermopylae Xerxes advanced into Attica and sacked Athens, but a few days later his fleet was defeated at the battle of Salamis. With control of the seas lost the Persians were in a dangerously exposed position in southern Greece and Xerxes decided to retreat back into Thessaly. He left his brother-in-law Mardonius in charge of the remaining army and then returned to Persia. Mardonius held on into the following year, but was then defeated and killed at Plataea, ending Xerxes's invasion of Greece.