In the Battle of Thermopylae, which occurred on August 19, 480 BC (and was detailed almost entirely by Herodotus), an alliance of Greek city-states fought the invading Persian Empire at the pass of Thermopylae in central Greece. Vastly outnumbered, the Greeks held back the Persians for three days in one of history's most famous last stands. A small force led by King Leonidas I of Sparta blocked the only road through which the massive army of Xerxes I of Persia could pass. After three days of battle, a local resident named Ephialtes is believed to have betrayed the Greeks by revealing a mountain path that led behind the Greek lines. Dismissing the rest of the army, King Leonidas stayed behind with 300 Spartans, 700 Thespian volunteers, 400 Thebans who had been pressed into service, and 900 Helots. Read more...