The document summarizes the Persian Wars between 500-479 BCE, where the Greek city-states defeated the mighty Persian Empire in a series of battles. It describes the key battles of Marathon, Thermopylae, Salamis, and Plataea, where significantly outnumbered Greek forces were able to defeat the massive Persian armies and navies. The victories established Athens as the most powerful city-state and helped spread democracy in Greece, while ensuring Persia would no longer invade.