command in the crucial victories of 480 and 479 BC. Over the next several years, however, Spartan leadership bred resentment among the Greek naval powers that took the lead in carrying the war against Persian territories in Asia and the Aegean, and after 478 BC the Spartans abandoned their leadership of this campaign. Sparta grew wary of Athens' strength after they had fought alongside each other to disperse the Persians from their lands. When Athens started to rebuild its walls and the strength of its naval power, Sparta and its allies began to fear that Athens was becoming too powerful. Different policies made it difficult for Athens and Sparta to avoid going to war, since Athens wanted to expand its territory and Sparta wanted to dismantle the Athenian democratic regime. Athens, meanwhile, had been asserting itself on the international scene, and was eager to take the lead in the Aegean. The Athenians had already rebuilt their walls, against the express wishes of Sparta. In 479 BC and 478 BC Athens also took a much more active role in the Aegean campaigning. In the winter of 479–478 BC they accepted the leadership of a new league, the Delian League, in a conference of Ionian and Aegean states at Delos. The Athenians rebuilt their walls in secret at the urging of Themistocles, who convinced the Athenians that this was the best way to protect themselves. Themistocles also delayed talks with Sparta for universal arms control by constantly finding issues with Sparta's proposals, stating that it would leave Athens vulnerable to Sparta's superior hoplites and phalanx fighting formation. After the completion of the walls Themistocles declared Athens independent of Spartan hegemony, stating that Athens knew what was in its best interest and was now strong enough to defend itself. At this time, one of the first hints of animosity between Athens and Sparta emerged in an anecdote reported by Diodorus Siculus, who said that the Spartans in 475–474 BC considered reclaiming the hegemony of the campaign against Persia by force. Modern scholars, although uncertain of the dating and reliability of this story, have generally cited it as evidence of the existence, even at this early date, of a "war party" in Sparta. For some time, however, friendly relations prevailed between Athens and Sparta. Themistocles, the Athenian of the period most associated with an anti-Spartan policy, was ostracised at some point in the late