Year 409 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Cossus and Medullinus (or, less frequently, year 345 Ab urbe condita). The denomination 409 BC for this year has been used since the early medieval period, when the Anno Dominicalendar era became the prevalent method in Europe for naming years.
The Athenian general, Thrasyllus, sails out from Athens with a sizable force to campaign in Ionia. There, he quickly captures Colophon and raids the Ionian countryside, but is defeated outside Ephesus by a combined Ephesian, Persian, and Syracusan force.
Taking advantage of the quarrels between the Greek cities in Sicily and of the mutual exhaustion of Athens and Syracuse, Carthage seeks to reimpose its influence over the island. Hannibal Mago, grandson of Hamilcar, invades Sicily with a strong force. He defeats the Sicilian Greeks and avenges his grandfather through the torture and killing of 3,000 Greek prisoners. He captures the cities of Selinus (modern Selinunte) and Himera, before returning triumphantly to Carthage with the spoils of war.