Final answer:
The forces of Philip of Macedon defeated the allied armies of Athens and Thebes at the Battle of Chaeronea in 338 BCE, marking a turning point in Greek history.
Step-by-step explanation:
In 338 BCE, at the Battle of Chaeronea, the forces of Philip of Macedon defeated the allied armies of Athens and Thebes. This victory allowed Philip to unite the Greek city-states under his leadership and pursue his goal of waging war against the Persian Empire. The Battle of Chaeronea marked a significant turning point in Greek history.