Excerpts from Books and Wikipedia
"To many of the fiercely independent city-states, Philip's power after 346 BC was perceived as a threat . . . In 340 BC Demosthenes convinced the Athenian assembly to sanction action against Philip's territories and to ally with the Achaemenids in Byzantium, which Philip was besieging. These actions were against the terms of their treaty oaths and amounted to a declaration of war. In summer 339 BC, Philip therefore led his army towards South Greece, prompting the formation of an alliance of a few southern Greek states opposed to him, led by Athens and Thebes. . . . The battle has been described as one of the most decisive of the ancient world. The forces of Athens and Thebes were destroyed . . . Philip was able to impose a settlement upon southern Greece, which all states accepted, with the exception of Sparta. The League of Corinth, formed as a result, made all participants allies of Macedon and each other . . . However, before he was able to take charge of the campaign, Philip was assassinated, and the Kingdom of Macedon and responsibility for the war with Persia passed instead to his son Alexander." [Wikipedia]