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
Greece in the 5th century BC in Attica, attempting to take Athens, but were defeated at the Battle of Marathon by a Greek army of 9000 Athenian hoplites and 1000 Plateans led by the Athenian general Miltiades. The Persian fleet continued to Athens but, seeing it garrisoned, decided not to attempt an assault. During the subsequent period of peace, in 483 BC, a silver-bearing seam had been discovered in the Laurion (a small mountain range close to Athens), and the hundreds of talents mined there had paid for the construction of 200 warships to fight Aegina's piracy. In 480 BC, Darius' successor Xerxes I sent a