Battle of Thermopylae

The Battle of Thermopylae was fought in the summer of 480 BC at a narrow coastal pass in central Greece, between the army of the Persian king Xerxes I and an alliance of Greek city-states led by King Leonidas I of Sparta. Over three days of fighting the outnumbered Greeks held the pass, until the Persians found a mountain path around it and destroyed the Greek rearguard. Although a Persian victory, it became one of the most celebrated last stands in history.

Athens and Eretria had helped the Ionian Revolt against Persian rule in 499–494 BC. In response, Darius the Great sent an expedition against Greece, which was defeated by the Athenians at the Battle of Marathon in 490 BC. A revolt in Egypt and then Darius's death delayed a second attempt, but his son Xerxes prepared a full-scale invasion, bridging the Hellespont and cutting a canal across the Athos peninsula. In 481 BC many Greek states, led by Athens and Sparta, formed a defensive alliance at Corinth.

On the advice of the Athenian Themistocles, the allies decided to block the Persian army at Thermopylae while their fleet held the nearby straits of Artemisium. Leonidas led roughly 7,000 men north, among them 300 Spartans. The size of the Persian force is one of the most disputed questions of ancient history. Herodotus, the main ancient source, claimed some 2.6 million fighting men, and other ancient writers gave figures from 800,000 to four million. Modern historians reject these numbers as impossible to supply and usually estimate between 120,000 and 300,000, though some suggest far fewer.

The exact date is uncertain, with scholars proposing dates from late July to September. On the first day Xerxes sent Median troops into the pass and then his elite Immortals, but in the confined space the Greek hoplites, fighting in close formation, threw both back with heavy losses. The second day brought no better result. That evening, according to Herodotus, a local man named Ephialtes told the Persians of a path over the mountain behind the Greek position, and the commander Hydarnes led a force along it overnight.

At dawn on the third day, Phocian troops guarding the path withdrew to a hill, and the Persians passed them by. Learning that he was about to be surrounded, Leonidas sent most of the allies away. He stayed with his Spartans, 700 Thespians who refused to leave, around 400 Thebans and probably the helots who served the Spartans, perhaps 2,000 men in all. Leonidas was killed by archers in the fighting that followed. Most of the Thebans surrendered, while the remaining defenders made a final stand on a small hill, where they were shot down. Excavations in 1939 found many Persian arrowheads on this hill.

Herodotus says that up to 20,000 Persians died, a figure that cannot be checked. He also gives a Greek total of 4,000 dead, which modern historians generally consider too high; a loss of around 2,000 is more often suggested.

With the pass lost, the Greek fleet withdrew from Artemisium to Salamis. The Persians overran Boeotia and Attica and took the evacuated city of Athens. Later in 480 BC, however, the Greek navy defeated the Persian fleet at the Battle of Salamis, and in 479 BC a Greek army defeated the Persian commander Mardonius at Plataea, ending the invasion. Thermopylae became a symbol of courage against overwhelming odds. A short verse usually attributed to the poet Simonides, telling passing strangers to inform Sparta that its men lay there obedient to its orders, was carved on a stone at the site.

Our 500 BCE map shows the Achaemenid Empire at the height of its power, a generation before Xerxes' invasion of Greece, an episode in the wider Greco-Persian Wars.