In what year did the Battle of Thermopylae take place?

The Battle of Thermopylae took place in 480 BC. It was fought between an alliance of Greek city-states, led by Sparta's King Leonidas I, and the invading Persian army of King Xerxes I.

The battle formed part of Xerxes' second Persian invasion of Greece, launched about a decade after the Persian defeat at Marathon in 490 BC. A Greek force of roughly 7,000 soldiers attempted to block the Persian advance at Thermopylae, a narrow pass between mountains and the sea. The position allowed the smaller Greek army to limit the advantage of Persia's much larger force.

For two days, the Greeks held the pass against repeated attacks. On the third day, a local resident named Ephialtes showed the Persians a mountain path that led behind the Greek position. Leonidas dismissed most of the Greek troops and remained with a smaller rear guard, including 300 Spartans and 700 Thespians, who were killed in the final stand.

Thermopylae was a Persian victory, although the Greek resistance became legendary. The battle occurred at the same time as the naval Battle of Artemisium. Later in 480 BC, the Greeks defeated the Persian fleet at Salamis, and in 479 BC they won the decisive Battle of Plataea.