He is best known for his political speeches on the need to defend Athens against the pretensions of Philip II of Macedon, which are known as the Philippics. Demosthenes was at the forefront of the campaign to unite the Greek city-states militarily against Macedon; the Greeks were defeated at the battle of Chaeronea in 338 bc, and Demosthenes committed suicide after the failure of an Athenian revolt against Macedon.