King Leonidas triumphed over the Persians in the Battle of Thermopylae

Explanation

Leonidas led his 300 Spartans, alongside around 700 Thespian volunteers, in a last stand against Xerxes' army, estimated at 80,000 to 200,000 men. Though it ended in a Persian victory, the three-day delay allowed Athens to be evacuated and the Greek fleet to concentrate at Salamis, setting the stage for the eventual Greek victories at Salamis and Plataea. The pass was only lost when a local Greek named Ephialtes betrayed a mountain path to the Persians.