The Samian War, a military conflict between Athens and Samos, is initiated by Athens' intervention in a dispute between Samos and Miletus.

The result is an Athenian victory; Samos surrenders.

The end of the revolts elsewhere in the Athenian empire, known formally as the Delian League, follows rapidly on this success.

Although Athens succeeds in restoring order to the empire, the situation in 440 BCE is very severe, particularly because of the threat of Spartan intervention.