It was a confederation of eastern Greek city-states, formedafter the defeat of the Persian invasion of mainland Greece 480-479BCE.After repelling the invasion, the Greek leading city-state,Sparta, proposed evacuating the Greeks under Persian rule from AsiaMinor to avoid recurrence of the revolution problems which hadsparked the war.Athens proposed an alternative - it would form a league of about180 of the affected city-states which would free them, backed bynaval forces supplied by Athens, from Persian control. This DelianLeague took its name from Delos, the island where its treasury topay for the defence forces was located.As time passed, members of the League tried to defect, or notpay their annual contribution. Athens ruthlessly enforce payment,sending out 100 warships each year to collect the money, by forcewhere necessary.When after 30 years, Persia agreed to peace, and to stay awayfrom the cities, Athens forced the cities to continue paying thewar funds. It moved the treasury to Athens and spent the money onthe warships which extorted the money, and on its own glorificationand public handouts. As Pericles admitted, Athens turned thisanti-Persian Empire league into an empire of its own.