"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 a Army of well over 100,000 men to Greece and was confronted by 300 Spartans, 700 Thespians and other Slave soldiers. Xerxes waited many days for King Leonidas to surrender or withdraw. When the Greeks did not leave, Xerxes was left with no option and he moved forward. The battle lasted for about 3 days and after which all 300 Spartans were killed. The Spartan defeat would not have happened if not for a local shepherd, named Ephialtes, who defected to the Persians and informed Xerxes of a separate path through Thermopylae, which the Persians could use to outflank the Greeks." -- Container.