Why was Thermopylae considered the most glorious defeat in Greek history?

The Battle of Thermopylae in 480 BCE is often regarded as the most glorious defeat in Greek history due to the valor and heroism displayed by the vastly outnumbered Greek forces, particularly the Spartans led by King Leonidas. Despite their ultimate defeat by the Persian army, the Greeks' stand at Thermopylae showcased their commitment to freedom and resistance against tyranny. This battle became a symbol of courage and sacrifice, inspiring future generations and unifying the Greek city-states against a common enemy. The narrative of their bravery transformed a loss into a powerful testament to the Greek spirit.