In the Battle of Thermopylae of 480 BC, an alliance of Greek city-states fought the invading Persian army in the mountain pass of Thermopylae. Vastly outnumbered, the Greeks held back the enemy in one of the most famous last stands of history. Persian King Xerxes lead an Army of over 100,000 men to Greece and was confronted by 300 Spartans. The battle lasted about 3 days, after which all 300 Spartans were killed. The Spartan defeat was not the one expected as a local shepherd named Ephialtes defected to the Persians and informed Xerxes of a separate path through Thermopylae, which the Persians could use to outflank the Greeks.