The Battle of Cyzicus in 410 B.C. was part of the Second Peloponnesian War between the Greek city states of Athens and Sparta and their allies. The Athenian commander Alcibiades won a decisive victory over the Peloponnesian fleet and a Persian army (who had allied with Sparta) in a combined land-sea operation in the Sea of Marmora. Sparts sued for peace after the battle based on the status quo, but Cleophon the demagogue had just seized power in Athens and refused, much to the future sorrow of the Athenians.
Encyclopedia of Military History, Dupuy & Dupuy, 1979