The battle of Thermopylae was a battle that took place in 480 B.C, on the coast of the Balkan Peninsula, between Greece and Persia.
King Xerxes and the Persians were trying to get to the Greek city-states and destroy them. King Leonidas and the Spartans fought against the Persians and pushed them back. The Spartans were winning the battle of Thermopylae, but one person caused the demise of the Spartans.
A Greek traitor confronted King Xerxes and told him about a secret way they could take to flank the Spartans. This traitor's name was Ephialtes, but not much is known about him, because the Persians claimed the idea to be their own, and the Greeks are too embarrassed to mention him.
The Persians used Ephialtes' plan. It worked, and the Greeks had to figure something out. King Leonidas sent everyone but the Spartans home, and the Spartans fought to the death. Everyone who stayed was killed by the Persians, the last Spartans were killed by a flurry of arrows.
The Persians made their way to Athens and burned it. The Athenians survived though, and later defeated the Persians at the Battle of Salamis.