How did Demosthenes oppose Philip II of Macedonia?

Demosthenes opposed Philip II of Macedonia primarily through his powerful oratory and political leadership in Athens, where he served as the head of the democratic faction. Recognizing Philip’s imperialistic ambitions early on, Demosthenes spent nearly 30 years attempting to rally the Athenians to defend Greek independence.1

His opposition included:

• Oratory: He delivered a series of famous speeches, most notably the "Philippics," in which he warned of Philip’s threats, criticized Athenian inaction, and urged his countrymen to take control of their own affairs. He also delivered the "Olynthiacs" to advocate for military aid to the city of Olynthus.12
• Political Reform: Demosthenes pushed for significant changes to Athenian policy, including naval reforms, to better prepare the city for conflict.1
• Diplomacy: He worked to build a grand alliance against Macedonia, successfully enlisting support from other Greek city-states, such as Thebes.1
• Direct Confrontation: He remained a staunch critic of pro-Macedonian figures in Athens, such as Aeschines, whom he accused of corruption and treachery for supporting Philip’s interests.1

Despite these efforts, the Greek alliance was ultimately defeated by Philip at the Battle of Chaeronea in 338 BCE.1