Siege of Eion - 475 B.C.
Eion is a town to the northeast of the Greek mainland which was a gateway to the important city of Amphipolis. It sits at the mouth of the Strymon River which flows into the Aegean from the interior of Thrace. It is referred to in Thucydides' History of the Peloponnesian War as a place of considerable strategic importance to the Athenians during the Peloponnesian War.
Eion was occupied by the Persians in 476 BC in the aftermath of the Persian Wars, but by 475 B.C. it was besiged by Kimon and the Delian League and the inhabitants were enslaved. The capture of Eion was the beginning of a military campaign undertaken by the newly formed Delian League, whose objective was to clear the Aegean Sea of Persian fleets and pirates in order to facilitate Athenian access to the Hellespont.
'The history of the Peloponnesian Wars' by Thucydidies (written c431 B.C),translated by Richard Crawley 1910.