Battle of Thermopylae
The Persian army marched into Greece under the leadership of King Xerxes. They encountered a small Greek force led by the Spartan commander Leonidas at a narrow mountain pass at Thermopylae. The Greeks were able to defend the pass against the much larger Persian forces until they were betrayed. A Greek traitor showed the Persians a secret passage around the pass. The Persians were able to attack from two sides. Realizing the battle was lost, Leonidas stayed back with 300 other Spartans to give time to the bulk of the Greek force to retreat safely. It was a tremendous act of sacrifice on the part of Leonidas and his fellow Spartans.