Expansion of Macedonia under Philip II a significant problem, blocking the main route into Greece. However, a second route into central Greece was available. In 480 BC, during the Battle of Thermopylae, the Persian king Xerxes had sent his army via a mountain track (the "Anopea") to outflank the pass. From this track, on the western side of Mount Kallidromon, another road led off and descended in Phocis. In 480 BC, a thousand Phocian troops were stationed above Thermopylae to guard the road and prevent a Persian assault on Phocis (though they notably failed to prevent the Persians using "Anopea"). However, in 339 BC, the Greeks
Thermopylae her older local cults, and perhaps a reference to the gates of Hades. A Greek myth mentioned that Heracles had jumped into the river in an attempt to wash off the Hydra poison infused in the cloak which he could not take off. The river has become hot and stayed that way ever since. Thermopylae is primarily known for the battle that took place there in 480 BC, in which an outnumbered Greek force probably of seven thousand (including the famous 300 Spartans, 500 warriors from Tegea, 500 from Mantinea, 120 from Arcadian Orchomenos, 1000 from the rest of Arcadia,