Delian League (dē`lēən), confederation of Greek city-states under the leadership of Athens. The name is used to designate two distinct periods of alliance, the first 478–404 B.C., the second 378–338 B.C. The first alliance was made between Athens and a number of Ionian states (chiefly maritime) for the purpose of prosecuting the war against Persia. All the members were given equal vote in a council established in the temple of Apollo at Delos, a politically neutral island, where the league's treasury was kept. The assessments to be levied on the members were originally fixed by Athens, and the fairness with which these were apportioned contributed much toward maintaining the initial enthusiasm. States contributed funds, troops, and ships to the league. After Persia suffered a decisive defeat at Eurymedon (468 B.C.), many members supported dissolution of the league. Athens, however, which had profited greatly from the league, argued that the danger from Persia was not over. When Naxos attempted to secede, Athens, taking the leadership from the assembly, forced (c.470 B.C.) Naxos to retain allegiance. Soon Thasos attempted the same maneuver and was likewise subdued (463 B.C.) by the Athenian general Cimon. The Athenians were so successful in their aims, using both force and persuasion, that by 454 B.C. the league had grown to c.140 members. An invasion by the league's enemies, Sparta and its supporters, was averted in 457 B.C., and Thebes, the traditional enemy of Athens, was subjected (456 B.C.). In 454 B.C., because of the real or pretended danger of Persian attack, the treasury was transported from Delos to the Athenian Acropolis. The league had in effect become an Athenian empire. However, its unity was not very stable, and in 446 B.C. Athens lost Boeotia. Gradually Athens lost its prestige as well as many of its alliances, and, with the Peloponnesian War (404 B.C.), the league came to an end. In 394 B.C., Conon reestablished the Athenian mastery of the sea at Cnidus. Proffers of alliance reached Athens, and in 378 B.C. the second Athenian confederacy was formed. Two years later Athens won a naval victory over Sparta near Naxos; the Athenians and Spartans compromised with a treaty that left Athens supreme on the sea and Sparta supreme on the mainland of Greece. In 371 B.C., Thebes withdrew from the alliance and gained predominance over Boeotian land that had been occupied (387 B.C.) by Sparta. A treaty was made between Athens and Sparta. By 351 B.C., however, the status of the league had been seriously weakened in the north and in the east, and in 338 B.C. the league was utterly destroyed by the victory of Philip II of Macedon in the battle of Chaeronea Chaeronea (kĕrənē`ə), ancient town of Boeotia, Greece, in the Cephissus (now Kifisós) River valley and NW of Thebes.
..... Click the link for more information. .

Delian League

Confederacy of ancient Greek states led by Athens and based on the island of Delos. Founded in 478 BC to combat Persia, its members included Aegean states and islands; Athens supplied commanders and assessed tributes of ships or money. It achieved a major victory in 467–466 when its fleet drove out Persian garrisons on the southern Anatolian coast. After 454 its leaders moved the treasury to Athens for safekeeping, used it to rebuild the city's temples, and treated the league as the Athenian empire. Most league members sided with Athens in the Peloponnesian War, which diverted the league from its Persian campaign. After defeating Athens in battle in 405, Sparta disbanded the league in 404. Fear of Sparta helped revive the league in the early 4th century, but it weakened as Sparta declined and was crushed by Philip II at the Battle of Chaeronea (338).