In 479 BC, the Greeks, under the Spartan Pausanias, defeated the Persian army at Plataea. The Athenian fleet then turned to chasing the Persians out of the Aegean Sea, defeating their fleet decisively in the Battle of Mycale, and in 478 BC the Athenian fleet captured Byzantium. In the course of doing so Athens enrolled all the island states and some mainland allies into an alliance, called the Delian League because the League's treasury was kept on the sacred island of Delos. The Spartans, although they had taken part in the war, withdrew from any further involvement, allowing Athens to become the unchallenged naval and commercial power in the region.