The Battle of Thermopylae was an epic battle which took place between the Greek city states led by King Leonidas of Sparta and the Achaemenid Empire led by Xerxes. The battle took place over the course of three days in late 480 BC. Ten years earlier, the Persians tried and failed to invade Greece. Xerxes then began building a massive army and navy with the goal to capture Greece once and for all. The Greek’s defense plan was to seal off the narrow pass at Thermopylae with their army of 7,000 men, blocking the Persian forces from entering. The Persians arrived soon after with approximately 150,000 soldiers. Although they were greatly outnumbered, the Greeks fought bravely for two long days before the Persians discovered a goat path which gave them access to the rear of the Greek’s formations. King Leonidas realized the end was near, so he dismissed the rest of the troops and remained to fight along with his group of 300 Spartans. Leonidas and his men fought to their deaths while allowing the others to escape. The Persians defeated the Greek defenses at Thermopylae and pushed on to capture the city of Athens.