The Delian League was founded in Athens in 478 BC as a military alliance to protect against the Persian Empire. The league was formed after the end of the Persian Wars and was originally composed of various Greek city-states and islands, which all agreed to contribute funds and military forces to protect against future Persian attacks. Athens emerged as the dominant power in the league and began using its position to advance its own interests, eventually transforming the alliance into an Athenian empire. Despite its initial purpose, the Delian League became a controversial and ultimately divisive force among the Greek city-states.