Eion (Ancient Greek: Ἠϊών; gen.: Ἠϊόνος) was an ancient Greek Eretrian colony in Thracian Macedonia specifically in the region of Edonis. 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.
Athenians for the first time attempted to capture Eion in 497 during the Ionian Revolt, which was unsuccessful as the revolt ended with Persians re-establishing control over the Thrace, including Eion, and a Persian fortress meant for permanent stay was built there, probably in 492 BC. Eion functioned as one of the main Achaemenid cities in Thrace where food was stored for the Persian king Xerxes I his great armies. Herodotus and Diodorus speak of "Persian" garrisons, of which the one at Eion was amongst them, which meant that its senior commander was apparently ethnically Persian. Xerxes had recalled most of the Persian troops from the area in the winter of 480/479 BC. It was then captured by the Delian League in 475 BC under the leadership of the Athenian general Cimon, the son of Miltiades the Younger, who started a siege on the city. Refusing Cimon's offer of an honorable withdrawal, the Persian commander Boges destroyed the treasure, killed his family, and committed suicide as the food ran out. Cimon turned the course of the River Strymon so that it flowed against the city walls, causing the mud brick fortifications to melt. 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.
In 424 BC, during the Peloponnesian War, Eion was the site where the Athenian commander Aristides intercepted a Persian messenger named Artaphernes. The message, which was on its way to Sparta, was a letter from the Persian king addressing previous requests made to him by the Spartans.
Later in the war, in the winter of 424 BC/423 BC, the Spartan general Brasidas captured Amphipolis with his Thracian allies. When he moved against Eion, however, he was unable to overcome the Athenian defenders, who were led by Thucydides. Although he held Eion, Thucydides was subsequently ostracized by the Athenians for his failure to defend the more pivotal city of Amphipolis.
- Keith G. Walker, Archaic Eretria: A political and social history from the earliest times to 490 BC (ISBN 0-415-28552-6), p. 154.
- Julia Valeva, Emil Nankov, Denver Graninger. "A Companion to Ancient Thrace" John Wiley & Sons, 15 jun. 2015. p 323
- Julia Valeva, Emil Nankov, Denver Graninger. "A Companion to Ancient Thrace" John Wiley & Sons, 15 jun. 2015. p 324
- Elspeth R. M. Dusinberre. "Empire, Authority, and Autonomy in Achaemenid Anatolia" Cambridge University Press, 2012. ISBN 1107018269 p 90
- Mogens Herman Hansen, An Inventory of Archaic and Classical Poleis: An Investigation Conducted by the Copenhagen Polis Centre for the Danish National Research Foundation, 2005, p. 827.
- Peter Edmund Laurent, The Nine Books of the History of Herodotus, Vol. 2 (Henry Slatter, 1837), p. 415.
- Gocha R. Tsetskhladze (ed.), Greek Colonisation: An Account of Greek Colonies and Other Settlements Overseas (Brill, 2008; ISBN 9004155767), p. 67.