Greek general Themistokles is pitted against the massive invading Persian forces, who are ruled by the god-king Xerxes and led by Artemisia, the vengeful commander of their navy. Knowing his only hope of defeating the Persian armada is to unite Greece, Themistokles leads the charge that will change the course of the war.

In the Battle of Thermopylae of 480 BC, an alliance of Greek city-states fought the invading Persian army in the mountain pass of Thermopylae. Vastly outnumbered, the Greeks held back the enemy in one of the most famous last stands of history. Persian King Xerxes lead an Army of well over 100,000 men to Greece and was confronted by 300 Spartans, 700 Thespians and other Slave soldiers. Xerxes waited many days for King Leonidas to surrender or withdraw....

In the 5th-century B.C., King Leonidas of Sparta has only his 300 bodyguards to stand with him against an invasion by the 60,000 men of the Persian army. Their heroic stand against the invasion gives the other Greek city-states time to organize a large fighting force and ultimately defeat the Persians.