All the Athenians had left was their fleet of ships, anchored in Salamis Bay. The Athenian fleet was based around fast-moving ships called triremes, which they planned to use against the Persians. The Athenians led a fleet of allied Greek ships at the Battle of Salamis, where they scored a massive naval victory over the much larger Persian fleet. This major victory elevated Athens to prominence among the Greek city-states, which the Spartans disliked, and thus they withdrew from the Greek alliance.(2)

After the Persians had been defeated and the Spartans had gone home, Athens and the other Greek city-states formed a new alliance at the Island of Delos in 477 BC. Accordingly, this new confederation was called the Delian League, and each city-state would contribute men, ships, and money to the League for protection.

As time progressed, Athens began to dominate the Delian league and took advantage of its allies' desire to stop sending ships and men. As a result, the members of the Delian league contributed money to the league rather than ships.(1)

This benefitted the Athenians greatly because it meant that they were increasing their military presence within the league, while the other members were weakening. Eventually, Athens moved the League treasure from Delos to Athens.

In doing so, they were able to use the money contributed by League members to expand their own military and economy, and essentially create an empire of puppet states that then had to pay tribute to Athens for protection from her military, as well as from the Persians.(3)