Sparta resented the growing power of Athens and sent an army into Boeotia. They defeated the Athenians at Tanagra in 457 BC but failed to take the city. Alarmed at the increasing hostility of Athens, several more of its allies tried to cede from the league. They were quickly hammered into submission.
Despite Spartan opposition, Athens continued to expand. In 454 BC, it moved the League's treasury from Delos to Athens itself. Marble lists of the tribute paid by League members survive on the Acropolis.
