The Greco-Persian Wars were a series of conflicts between the ancient Greek city-states and the vast Persian Empire that took place in the 5th century BCE. The wars began in 499 BCE when the Greek city of Miletus revolted against Persian rule, leading to a series of battles. Notable events include the famous Battle of Marathon in 490 BCE, where the Athenians achieved a surprising victory against the Persians. The conflict escalated with the invasion of Greece by Persian King Xerxes I in 480 BCE. Key battles during this phase included the heroic stand of the Spartans at the Battle of Thermopylae and the decisive naval victory at the Battle of Salamis.