- The Persians under Darius II see their opportunity to play off one Greek city-state against another and to recover control of the Greek cities of Asia Minor, which have been under Athenian control since 449 BC. The satraps of Asia Minor, Tissaphernes and Pharnabazus, are ordered to collect overdue tribute.
- The Spartans sign a treaty of mutual help with the Persian satrap of Lower Asia, Tissaphernes. By the treaty of Miletus, Persia is given complete freedom in western Asia Minor in return for agreeing to pay for seamen to man the Peloponnesian fleet.
- Alcibiades helps stir up revolts amongst Athens' allies in Ionia, on the west coast of Asia Minor. However, Alcibiades loses the confidence of the Spartans and antagonises their king Agis II. As a result, he flees to the court of the Persian satrap Tissaphernes. Alcibiades advises Tissaphernes to withdraw his support from Sparta while conspiring with the oligarchic party in Athens, as Sparta's allied cities break away in a series of revolts.
- The Athenians vote to use their last reserves to build a new fleet.
- Clazomenae revolts against Athens. After a brief resistance, however, it again acknowledges the Athenian supremacy.