Based on Frank Miller's graphic novel, 300 is very loosely based the 480 B.C. Battle of Thermopylae, where the King of Sparta led his army against the advancing Persians; the battle is said to have inspired all of Greece to band together against the Persians, and helped usher in the world's first democracy. In the ancient battle of Thermopylae, King Leonidas and 300 Spartans fight against Xerxes and his massive Persian army. They face insurmountable odds when they are betrayed by a Spartan reject.