Only twenty years before the First Peloponnesian War broke out, Athens and Spartans had fought alongside each other in the Greco-Persian Wars. In that war, Sparta held hegemony over what modern scholars call the Hellenic League and the overall 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.