Delian_League The Delian League () was an association of approximately 150 5th-century BC Greek city-states under the leadership of Athens, whose purpose was to continue fighting the Persian Empire after the Greek victory in the Battle of Plataea at the end of the Greco–Persian Wars. Founded in 478 BC, the League's name derives from its official meeting place, the island of Delos, where congresses were held in the temple and where the treasury stood until Pericles moved it to Athens in 454 BC.