 The Persian king of kings Xerxes has devoted his reign to realizing the ambition of his father, stopped by Greeks, to extend his Achaemenid slave empire to and beyond Greece, and marches in 480 BC with an unprecedentedly vast army. When a captured Spartan explorer shows unconditional courage even on the chopping block, he is spared and send to the assembled Greek states at Corinth to report the Persian might. There the Athenian leader Themistocles manages to turn the defeatist tide by formally placing the Athenian fleet under the supreme command of Sparta, whose king Leonidas promises to defend Greece regardless who follows- but back in Sparta, the ruling council hesitates to commit the whole army until the Persians approach the Corinthian Isthmus, and even after an encouraging Delphi oracle -loose a king or all Sparta- is forbidden to lead it before the end of a religious festival, so he takes off first, keeping his promise, with only his 300 mean strong bodyguard. Realizing there is no time to wait for sufficient reinforcements, but abandoning the northern access to Greece proper may allow the Persian to swarm the country before it can make a proper stand, he decides to take a heroic suicidal stand: fight impossible odds till the last man at the narrow pass of Thermopylai to minimize the numeric disadvantage, in the hope this will buy enough time. They prove Spartans deserve the reputation of fiercest and best-disciplined fighters, ingeniously creating the element of surprise and driving the over-confident aggressor to growing despair by inflicting humiliating losses at every failing attack wave, even by the imperial body guard of 10,000  immortals . Just when Xerxes plans to return faking a divine message, the traitor Ephialtes arrives...