Thermopylae & the 300
The Second Persian Invasion
Marathon had humiliated Persia but not ended the threat. Darius died before he could launch a second invasion, and his son Xerxes inherited both the throne and his father’s ambition to conquer Greece. In 480 BC, Xerxes assembled the largest army ever to march against a Greek city-state. Ancient sources give famously large numbers — Herodotus speaks of over a million men — but modern estimates put the total force at something like 100,000 to 300,000. Whatever the exact count, the Greek cities knew they were facing something unprecedented.
The Greek city-states that chose to resist — led by Sparta on land and Athens at sea — formed a defensive alliance. The strategy was to hold a series of narrow chokepoints where Persian numbers would count for less. The first and most famous of these was the narrow coastal pass of Thermopylae, meaning “the Hot Gates” after the warm sulphur springs nearby. At its narrowest, the pass was only wide enough for a wagon — perhaps fifteen to twenty metres across — between the mountains and the sea.
Leonidas and the Greek Defenders
The Greek force sent to hold Thermopylae was led by Leonidas, one of Sparta’s two kings. He brought three hundred Spartan hoplites — the famous Three Hundred — each selected from men who had already fathered sons, so that their family lines would not be extinguished. Alongside the Spartans were thousands of other Greek troops: Thespians, Thebans, Phocians and others. Ancient sources give totals of around four thousand to seven thousand Greek fighters in total at the start.
The Greek plan was tactically sound. In such a narrow pass, a Persian cavalry charge was impossible and the vast Persian infantry could only engage a small number of men at a time. The Spartan hoplites, supremely trained and with the advantage of the ground, held the pass for two days of fierce fighting against repeated Persian assaults. Herodotus describes the Persians suffering enormous casualties trying to force their way through, including the elite Persian infantry known as the Immortals. The stand lasted three days in total: two days of fighting in the pass, followed by a third day of last-stand fighting after Ephialtes' betrayal allowed the Persians to outflank the position.
Leonidas led three hundred Spartans at Thermopylae, each selected because he had already fathered sons. The Greeks held the pass for three days in total: two days of fighting, then a third day of the last stand after Ephialtes revealed the mountain path. Persian numbers were neutralised by the narrow ground during those first two days.
The Betrayal by Ephialtes
The Greek position was broken not by force but by treachery. A local man named Ephialtes approached Xerxes and revealed the existence of a mountain path called the Anopaea track, which wound around behind the Greek position. Xerxes sent his Immortals along this route during the night. The Phocian troops posted to guard the path were surprised and driven back.
Leonidas received word of the flanking movement before dawn. He knew the position was now untenable: to stay meant encirclement and death for all. He dismissed the majority of the Greek allied forces — ordering them to withdraw and fight another day. He kept the three hundred Spartans, a contingent of Thespians who chose to remain of their own free will, and the Theban contingent, who may have been detained against their will as they were politically suspect.
The Last Stand
The final day at Thermopylae was a deliberate sacrifice. Leonidas led his rearguard forward beyond the wall they had been defending — into the wider part of the pass — fighting in the open to kill as many Persians as possible before being overwhelmed. Herodotus describes the Greeks fighting with their spears until the shafts broke, then drawing their swords, and finally using their hands and teeth. Leonidas himself was killed in the fighting.
Xerxes was so angry at the Greek resistance — and so personally offended by Leonidas — that he had the Spartan king’s body decapitated and his head displayed on a pole, a treatment of corpses considered deeply dishonourable in both Greek and Persian tradition. The ancient sources note this as evidence of how unusual and humiliating the Spartan resistance had been for the Great King.
Two other figures become emblematic of the battle in Herodotus’s account. Demaratus was a deposed Spartan king living at the Persian court as an adviser. He famously tried to explain to Xerxes why the Spartans would not surrender: they feared their law more than they feared any man. Xerxes did not believe him. The exchange illustrates perfectly the Persian inability to understand the Spartan warrior culture.
The Spartan warrior Dienekes became famous for a response reported by Herodotus. When told that the Persian archers were so numerous that their arrows would block out the sun, Dienekes allegedly replied that this was good news, since the Greeks would be fighting in the shade. Whether the anecdote is true or not, it was remembered and retold because it perfectly captured the Spartan attitude of contemptuous indifference to odds.
Visual Evidence: the Bronze Warrior Figure and the Helmet at Olympia
The two prescribed visual sources for this period illuminate different aspects of the conflict. The Spartan bronze warrior figure in the British Museum (1929,1016.6), a small votive figurine showing a warrior in forward motion, represents the spirit that Leonidas embodied: aggressive, compact, full of controlled energy. It was made in Sparta as a dedication to a deity, reflecting the way Spartan warrior culture was woven into religious practice.
The Corinthian-type helmet dedicated at Olympia, now in the British Museum, is similarly relevant. The dedication of captured or retired armour at Panhellenic sanctuaries was a way of thanking the gods for military victories and advertising your city’s martial success to all of Greece. The sanctuaries of Olympia and Delphi accumulated enormous quantities of such dedications after the Persian Wars, turning them into permanent monuments to Greek resistance.
Thermopylae fell because Ephialtes, a Greek traitor, revealed a mountain path (the Anopaea track) that allowed Xerxes to send his Immortals around the pass. Without this betrayal, the narrow ground might have held for much longer. This is why Ephialtes became a byword for treachery in Greek memory.
Though the battle was a military defeat, Thermopylae was immediately transformed into a moral victory. The Spartans and Thespians who died were commemorated in an inscription on a memorial stone, attributed to the poet Simonides, whose words (paraphrased) ran: “Go, tell the Spartans, passer-by, that here, obedient to their laws, we lie.” This epitaph is one of the most famous in ancient literature and encapsulates the Spartan value of dying in obedience to the law rather than retreating.
The strategic significance of the battle was equally important. By holding the pass for three days, the Greek defenders allowed the Athenian fleet to withdraw safely from its position at Artemisium and regroup for the decisive naval engagement at Salamis. The sacrifice of Leonidas and his Three Hundred was therefore not merely symbolic: it bought Greece the time it needed.