Battle of Thermopylae 480 BC: 300 Spartans' Epic Last Stand King Leonidas led 300 Spartans—plus 6,000-7,000 Greek allies—to hold the narrow Thermopylae pass against Xerxes I's massive Persian invasion force of 100,000 during the Second Persian War. For three days, Greek hoplite phalanxes exploited the bottleneck terrain, slaughtering waves of Medes and Immortals while rotating fresh ranks to maintain unbreakable cohesion. Unyielding Defense Spartan bronze shields, 8ft spears, and short swords ou