Delian League

The Delian League was founded in 478 BC. It was an association of Greek city-states under the leadership of Athens. The League had a many cities: at various times between 150 and 330.The Complete Idiot's Guide to Ancient Greece By Eric D. Nelson, Susan K. Allard-Nelson, Susan K. Allard-Nelson. p. 197.Streams of Civilization: Earliest Times to the Discovery of the New World By Mary Stanton, Albert Hyma. p. 125 

The League was led by Athens to continue fighting the Persian Empire. The Greeks had won the Battle of Plataea at the end of the Second Persian invasion of Greece. 

The League's modern name comes from its official meeting place, the island of Delos, where congresses were held in the temple. The treasury stood there, until Pericles moved it to Athens in 454 BC.Eva C. Keuls, The Reign of the Phallus: Sexual Politics in Ancient Athens (Berkeley: University of California Press) 1985:18.A history of the classical Greek world: 478-323 BC By Peter John Rhodes p. 18  (2006) In ancient sources,  there is no special designation for the league and its members as a group are simply referred to with phrases along the lines of "the Athenians and their allies". See Artz, James. 2008. The Effect of Natural Resources on Fifth Century Athenian Foreign Policy and the Development of the Athenian Empire. Saarbrücken, VDM Verlag. p. 2

Soon after the League was set up, Athens began to use the League's funds for its own purposes. This led to conflict between Athens and the less powerful members of the League. By 431 BC,  the League presented a threat to Sparta. This, and Athens's heavy-handed control of the League, started the Peloponnesian War. The League was dissolved after the war's end in 404 BC by the order of Lysander, the Spartan commander.

 References 

Category:1st-millennium BC establishments
Category:5th-century BC establishments
Category:Ancient Greek cities