In this retelling of the Battle of Thermopylae, King Xerxes of Persia amasses an army of hundreds of thousands to conquer the divided nation of Greece in 481 B.C. In the mountain pass of Thermopylae, they encounter Spartan King Leonidas and his royal guard of soldiers numbering just 300. According to legend, their valor and sacrifice inspired all of Greece to unite against the Persian foe.