Answer
Killed in battle, Leonidas I, the legendary Spartan king, met his end during the Battle of Thermopylae in 480 BC. Leading a force of 300 Spartans against the overwhelming Persian army, Leonidas and his men held off the invaders for three days, ultimately sacrificing themselves to ensure the retreat of the Greek forces. Their heroic stand became a symbol of Spartan valor and discipline, inspiring generations to come.