In 478 BC, following the defeat of Xerxes' invasion of Greece, Pausanias the Spartan led Hellenic forces against the Persians. He was an unpopular commander (who may have conspired with the Persians), and Sparta was eager to stop prosecuting the war. They surrendered the leadership of the ongoing campaign to Athens, which was eager to accept it. The Delian League was inaugurated in 477 BC as an offensive and defensive alliance against Persia. The principal cities in the League were Athens, Chios, Samos, and Lesbos, but many of the principal islands and Ionian cities joined the league.
Athens led the Delian League from the beginning, though at its founding the treasury was located on the island of Delos, and each state in the league had an equal vote. The assessment due from each state was assigned by Aristides the Just, leader of the Athenians; some members were assessed ships, others troops, others weapons, and others money. A council of all the cities met at Delos regularly, probably when bringing their assessment to the island.
The first action of the Delian League, under the command of Cimon, was the capture of Eion, a Persian fortification that guarded a river crossing on the way to Asia; following this victory, the League acted against several pirate islands in the Aegean Sea, most notably against Scyros where they turned the Dolopian inhabitants into slaves, and Athens set up a settler-colony (known as a cleruchy). A few years later they sailed against Caria and Lycia, defeating both the Persian army and navy in the battle of the Eurymedon.
These actions were most likely very popular with the League's members. However, the League, particularly the Athenians, were willing to force cities to join or stay in the League. Carystus, a city on the southern tip of Euboea, was forced to join the League by military actions of the Athenians. The justification for this was that Carystus was enjoying the advantages of the League (protection from pirates and the Persians) without taking on any of the responsibilities. Furthermore, Carystus was a traditional base for Persian occupations. Athenian politicians had to justify these acts to Athenian voters in order to get votes. Naxos, a member of the Delian League, attempted to secede, and was enslaved; Naxos is believed to have been forced to tear down her walls, lost her fleet, and her vote in the League.
Thucydides tells us that this is how Athens' control over the League grew.
Of all the causes of defection, that connected with arrears of tribute and vessels, and with failure of service, was the chief; for the Athenians were very severe and exacting, and made themselves offensive by applying the screw of necessity to men who were not used to and in fact not disposed for any continuous labor. In some other respects the Athenians were not the old popular rulers they had been at first; and if they had more than their fair share of service, it was correspondingly easy for them to reduce any that tried to leave the confederacy. The Athenians also arranged for the other members of the league to pay its share of the expense in money instead of in ships and men, and for this the subject city-states had themselves to blame, their wish to get out of giving service making most leave their homes. Thus while Athens was increasing her navy with the funds they contributed, a revolt always found itself without enough resources or experienced leaders for war. [Thucydides i. 99]
In 454 BC, Athens moved the treasury of the Delian League from Delos to Athens, allegedly to keep it safe from Persia. However, Plutarch indicates that many of Pericles' rivals viewed the transfer as Athens usurping...