The Greeks and Persians went to war with each other because of the existence of Greek colonies in Asia Minor that had become part of the Persian Empire. Greek cities in Asia Minor had become Persian subjects in the mid-sixth century BC. Many of these cities were rebelling against the Persians because of their dislike of the Persian form of government. Persia was an empire that did not give its subjects the same kinds of freedoms that the Greek poleis typically did. Some city-states from mainland Greece helped the cities in Asia Minor rebel. This led to the Persian Wars.