At age 16, (340BC) King Philip waged war on Byzantium and left Alexander as regent. During this time, the Thracian Maedi tribe revolted against Macedonian rule. Alexander quickly responded by driving them from their territory and recolonizing it with Greeks. He founded a city, Alexandropolis. When Philip returned he dispatched Alexander to deal with revolts in southern Thrace which Alexander did successfully.
Meanwhile, the citizens of Amphilla began working the lands sacred to the Oracle at Delphi. This was considered sacrilege and gave Philip the opportunity to intervene in Greek affairs. Philip occupied himself with Thrace while Alexander mustered an army which was supposedly for an attack against the Illyrians while in reality it was meant for southern Greece. During this time, the Illyrians invaded Macedonia only to be repelled by Alexander.
In 338BC, King Philip and his son Alexander made war on Greece. They defeated the Greek coalition at the battle of Chaeronia and established a Hellenic Alliance at Corinth with Macedonia at its head.
Then in 337BC, Philip married a second woman: Cleopatra Eurydice. This made Alexander's mother, Olympias crimson with rage and jealousy. In 336BC, while atttending a wedding in Aegae, Philip was murdered by his bodyguard Pausanias (With the instigation of Olympias). Alexander then succeeded him as king of Macedonia.
Following Philip's death, Thebes revolted against Alexander. He crushed the revolt and returned home. Meanwhile, Olympias had Cleopatra Eurydice and her daughter (Cleopatra's) Europa burnt to death.
Following the consolidation of his power, Alexander began a Balkan campaign which ended the following year.