power. Additionally, the Spartans were of the view that, with the liberation of mainland Greece, and the Greek cities of Asia Minor, the war's purpose had already been achieved. There was also perhaps a feeling that establishing long-term security for the Asian Greeks would prove impossible. In the aftermath of Mycale, the Spartan king Leotychidas had proposed transplanting all the Greeks from Asia Minor to Europe as the only method of permanently freeing them from Persian dominion. Xanthippus, the Athenian commander at Mycale, had furiously rejected this; the Ionian cities had been Athenian colonies, and the Athenians, if no one else, would protect the Ionians. This marked the point at which the leadership of the Greek alliance effectively passed to the Athenians. With the Spartan withdrawal after Byzantion, the leadership of the Athenians became explicit. The loose alliance of city states which had fought against Xerxes's invasion had been dominated by Sparta and the Peloponnesian league. With the withdrawal of these states, a congress was called on the holy island of Delos to institute a new alliance to continue the fight against the Persians; hence the modern designation "Delian League". According to Thucydides, the official aim of the League was to "avenge the wrongs they suffered by ravaging the territory of the king." In reality, this goal was divided into three main efforts—to prepare for future invasion, to seek revenge against Persia, and to organize a means of dividing spoils of war. The members were given a choice of either offering armed forces or paying a tax to the joint treasury; most states chose the tax. League members swore to have the same friends and enemies, and dropped ingots of iron into the sea to symbolize the permanence of their alliance. The Athenian politician Aristides would spend the rest of his life occupied in the affairs of the alliance, dying (according to Plutarch) a few years later in Pontus, whilst determining what the tax of new members was to be. Members Composition and expansion In the first ten years of the league's existence, Cimon/Kimon forced Karystos in Euboea to join the league, conquered the island of Skyros and sent Athenian colonists there. Over time, especially with the suppression of rebellions, Athens exercised hegemony over the rest of the league. Thucydides describes how Athens's control over the League grew: Of all the causes of defection, that connected with arrears of tribute