What was the outcome of the Battle of Thermopylae?

The Battle of Thermopylae ended in a Persian victory. In 480 BC, the army of Xerxes I broke through the Greek defensive position after a local man, Ephialtes, revealed a mountain path leading behind the pass.

Leonidas and the Greek defenders had held the narrow position for two days, where the terrain limited the Persians’ numerical advantage. Once the Greeks were outflanked, Leonidas sent most of the allied army away. He stayed behind with the 300 Spartans, 700 Thespians, and other defenders, who were eventually surrounded and killed.

The Persian victory opened the route into central Greece. Xerxes’s forces captured and burned Athens, which had been evacuated, although the Greek resistance continued. Later in 480 BC, the Greek fleet defeated the Persians at Salamis, and in 479 BC a Greek army won at Plataea. Those later victories helped end the invasion, but they do not change the outcome at Thermopylae itself.