At Thermopylae, a narrow coastal pass in central Greece, King Leonidas and a force built around 300 Spartans held a chokepoint against the invading Persian army of Xerxes for seven days before being surrounded and wiped out. The film reconstructs the battle through the terrain itself, walking the pass to show why a small, disciplined force could bottleneck a vastly larger one, and lays out the political backdrop that brought Persia into Greece in the first place. Historians and battle reenactments cover the phalanx tactics, the betrayal by Ephialtes that let Persian troops flank the defenders, and the final stand once retreat was no longer possible. The film treats the episode as both military history and myth-making, tracing how the Spartan defeat was turned almost immediately into a rallying story for the rest of Greece. It stays focused on the mechanics of the battle rather than lingering on legend, using the landscape and ancient accounts to explain how so few held off so many for as long as they did.