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
Battle of Thermopylae by Leonidas (Herodotus admits that there is some doubt about which actually happened). The contingent of 700 Thespians, led by their general Demophilus, refused to leave and committed themselves to the fight. Also present were the 400 Thebans and probably the helots who had accompanied the Spartans. Leonidas' actions have been the subject of much discussion. It is commonly stated that the Spartans were obeying the laws of Sparta by not retreating, but it seems it was actually the failure to retreat from Thermopylae that gave rise to the notion that Spartans never retreated. It is also possible that, recalling