The Persians failed to conquer the Greek mainland in 479 B.C. After that, the Persian Empire and its Achaemenid leaders began to lose power. The kings who followed Xerxes were weak rulers.
At the same time, the Greek city-states grew stronger after Philip of Macedonia organized them into the Hellenic League. He named himself and his descendants leaders of the league. Philip was murdered in 336 B.C. Soon after that, in 334, his son, Alexander, decided to invade Persia. He was later known as Alexander the Great.
