Persia, a powerful empire to the East, had attacked Greece in 480 BC. The Persian army had destroyed Athens. King Philip of Macedon had been made leader of all the Greek poleis so that he could punish the Persians. Before his armies set off to fight, Philip organised a special festival to honour the Olympic gods. During this festival, he was murdered.
Some said he was murdered because he disrespected the gods by saying he was a god himself. Others said that he was murdered because people wanted his son Alexander to be king. Alexander did become king. He was only twenty years old.
In 336 BC, Alexander led the attack on Persia. The Persian army tried its best to stop him, but Alexander and his strong, efficient army won the battle.