Following the Persian Wars, what were the steps that Athens took to become an empire?

The Delian League was formed to continue fighting the Persian Empire after Persia's invasions were finally defeated. In 454 BC, Pericles moved the treasury of the Delian League from Delos to Athens. This proved that Athens completely controlled the Delian League, and effectively began the Athenian Empire. While the Athenians continued to gain power by expanding and creating colonies that were dependent on them, the Spartans began to consolidate power and even allied with the Persians as a way to counteract Athenian control.