480 BCE

In The Battle of Thermopylae of 480 BC, an alliance of Greek city-states fought the invading Persian Empire at the pass of Thermopylae in central Greece. Vastly outnumbered, the Greeks held back the Persians for three days in one of history's most famous last stands.

A small force led by King Leonidas of Sparta blocked the only road through which the massive army of Xerxes I could pass. After three days of battle, a local resident named Ephialtes betrayed the Greeks by revealing a mountain path that led behind the Greek lines. Dismissing the rest of the army, King Leonidas stayed behind with 300 Spartans and 700 Thespian volunteers. The Persians succeeded in taking the pass but sustained heavy losses, extremely disproportionate to those of the Greeks.

The fierce resistance of the Spartan-led army offered Athens the invaluable time to prepare for a decisive naval battle that would come to determine the outcome of the war. The subsequent Greek victory at the Battle of Salamis left much of the Persian Empire's navy destroyed and Xerxes I was forced to retreat back to Asia, leaving his army in Greece under Mardonius, who was to meet the Greeks in battle one last time. The Spartans assembled at full strength and led a pan-Greek army that defeated the Persians decisively at the Battle of Plataea, ending the Greco-Persian War and with it the expansion of the Persian Empire into Europe.

Influence
The Spartans in Halo are named after these Ancient Spartan Warriors, taught how to fight like a pack of wolves, using teamwork to whittle down single enemies. From Halo: Fall of Reach's training segment.

Parallels
It is believed by many fans that Halo 3 will end similar to the Battle of Thermopylae, with the Master Chief as Leonidas, the 300 Spartans paralleled by the remaining Spartan-II and Spartan-III, and the 700 Thespians by allied Elites. All giving their lives against hordes of Covenant loyalists, buying time for humans (and possibly aliens) setting off the Halos, and then seeking refuge in the Shield World. The decisive Naval battle paralleled by either UNSC and Former Covenant allying against the remaining Covenant, or the Halos' activation.