<P> The first member of the league to attempt to secede was the island of Naxos in c. 471 BC . After being defeated, Naxos is believed (based on similar, later revolts) to have been forced to tear down its walls, and its lost its fleet and its vote in the League . </P> <P> In 465 BC, Athens founded the colony of Amphipolis on the Strymon river . Thasos, a member of the League, saw her interests in the mines of Mt . Pangaion threatened and defected from the League to Persia . She called to Sparta for assistance but was denied, as Sparta was facing the largest helot revolution in its history . </P> <P> An aftermath of the war was that Cimon was ostracised, and the relations between Athens and Sparta turned hostile . After a three - year siege, Thasos was recaptured and forced back into the League . The siege of Thasos marks the transformation of the Delian league from an alliance into, in the words of Thucydides, a hegemony . </P> <P> After two years Thasos surrendered to the Athenian leader Cimon . In result, the fortification walls of Thasos were torn down, their land and naval ships were confiscated by Athens . The mines of Thasos were also turned over to Athens, and they had to pay yearly tribute and fines . </P>

Athens moves the delian league's treasury to the acropolis