History of the Peloponnesian War

The next summer the truce for a year ended, after lasting until the Pythian games. During the armistice the Athenians expelled the Delians from Delos, concluding that they must have been polluted by some old offense at the time of their consecration, and that this had been the omission in the previous purification of the island, which as I have related, had been thought to have been duly accomplished by the removal of the graves of the dead. The Delians had Atramyttium in Asia given them by Pharnaces, and settled there as they removed from Delos.

Meanwhile Cleon prevailed on the Athenians to let him set sail at the expiration of the armistice for the towns in the direction of Thrace with twelve hundred heavy infantry and three hundred horse from Athens, a larger force of the allies, and thirty ships.