"The Delian League (or Athenian League) was an alliance of Greek city-states led by Athens and formed in 478 BCE to liberate eastern Greek cities from Persian rule and as a defense to possible revenge attacks from Persia following the Greek victories at Marathon, Salamis, and Plataea in the early 5th century BCE. The alliance of over 300 cities would eventually be so dominated by Athens that, in effect, it evolved into the Athenian empire. Athens became increasingly more aggressive in its control of the alliance and, on occasion, constrained membership by military force and compelled continued tribute which was in the form of money, ships or materials. Following Athens’ defeat at the hands of Sparta in the Peloponnesian War in 404 BCE the League was dissolved."
