Delian League dē´lēən [key], 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 BC, the second 378–338 BC 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 BC), 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 BC) Naxos to retain allegiance. Soon Thasos attempted the same maneuver and was likewise subdued (463 BC) by the Athenian general Cimon. The Athenians were so successful in their aims, using both force and persuasion, that by 454 BC the league had grown to c.140 members. An invasion by the league's enemies, Sparta and its supporters, was averted in 457 BC, and Thebes, the traditional enemy of Athens, was subjected (456 BC). In 454 BC, 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 BC Athens lost Boeotia. Gradually Athens lost its prestige as well as many of its alliances, and, with the Peloponnesian War (404 BC), the league came to an end. In 394 BC, Conon reestablished the Athenian mastery of the sea at Cnidus. Proffers of alliance reached Athens, and in 378 BC 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 BC, Thebes withdrew from the alliance and gained predominance over Boeotian land that had been occupied (387 BC) by Sparta. A treaty was made between Athens and Sparta. By 351 BC, however, the status of the league had been seriously weakened in the north and in the east, and in 338 BC the league was utterly destroyed by the victory of Philip II of Macedon in the battle of Chaeronea.
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