In an aggressive campaign never seen before on Earth, Philip II took the crown of Macedonia in 358BC after deposing his 1 year old nephew Amyntus IV. He was opposed by Boeotia, the present superpower, Athens, long past its' glory, and Persia, which has had failed campaigns 
against Greece and Macedonia. He managed to pay them off, and immediately rebuilt the entire kingdom, conquered Thrace, Chalcidice, Potidea (a Spartan colony), and Olynthus (the war was opposed strongly by Athens). By 352BC, he reached Thermopylae, the gateway to the main part of Greece, but didn't attempt to take it because the Athenians had strongly defended it.