The Greco-Persian Wars were a series of conflicts between the Persian Empire and Greek city-states from 490 BC to 479 BC. Key battles included the Persians defeating the Greeks at Eretria but the Greeks winning at Marathon. Over a decade later, Xerxes led a massive Persian invasion of Greece but the Greeks were victorious at Thermopylae, Salamis, and Plataea. The wars resulted in Greek independence and the formation of the Delian League led by Athens for mutual defense against Persia.