The Greeks viewed the northern neighbors, the Macedonians, as barbarians. The Macedonians were actually rural people in groups but not in city-states like the Greeks.
However, by the end of the fifth century, B.C. Macedonia emerged powerful as a kingdom.
A great admirer of the Greek culture, Philip II wanted to unite all the Greek polis under Macedonia
The Athenians allied with other city-states fearing that Philip II would become a threat. The Macedonians crushed their army and they were left surprised. This took place in Thebes, 338 B.C. and was called the Battle of Chaeronea.
Philip II quickly brought an end to the freedom of the Greek city-states. Having united Greece, he decided to form a league and go into war against the Persians.
Before being assassinated, Philip II tried to undertake an invasion on Asia. His son took over the mantle, Alexander would be known as the Great for accomplishing a lot like fulfilling his father's dream to invade the Persians.