The eastern Greek allies revolt from Spartan control toward the end of 478 and at Delos offer their allegiance, through Aristides, to Athens.
The new alliance, established on the basis of equality of its members, convenes on the island of Delos, sacred to Apollo.
The original organization of the league, as sketched by Thucydides, indicates that all Greeks were invited to join to protect themselves from Achaemenian Persia.
Athens is in fact interested in further supporting the Ionians in Anatolia and exacting retribution from the Persians, whereas Sparta is reluctant to commit itself heavily overseas.
The Athenians are to supply the commanders in chief and to decide which states are to provide ships or money; money is to be received and controlled by ten Athenian treasurers (hellenotamiai).
Representatives of all member states, each with equal vote, are to meet annually at Delos, where the league's treasury is kept in the temple of Apollo.
The original membership probably includes most of the Aegean islands, except Aegina, Melos, and Thera, most of the cities of Chalcidice, the shores of the Hellespont and Bosporus, some of Aeolia, most of Ionia, and a few eastern Dorian and non-Greek Carian cities.
Apart from the big Ionian islands and some mainlanders, there are in fact Dorian members like Rhodes and Aeolians like Lesbos; there even are some non-Greeks on Cyprus, always a place with a large Semitic component. (Some Cypriot communities probably join at the outset.)
Some Thracian cities are surely enrolled very early.
Aristides, who is with Cimon one of the chief architects of the League, is chosen to assess the contributions to be paid by the member state; some contribute ships and men instead of money.
