Passage: In the revived democracy established in 403 BC, Thrasybulus became a major and prestigious leader, although he was soon superseded at the head of the state by Archinus.  Thrasybulus seems to have advocated a more radically democratic policy than the populace was willing to accept at the time; he called for reinstating pay for political service, and sought to extend citizenship to all the metics and foreigners who had fought alongside him against the Thirty.  He was initially cautious about offending Sparta, but, when Persian support became available at the start of the Corinthian War, he became an advocate of aggressive action, and about this time seems to have regained his preeminence in Athenian politics.  He initiated the rebuilding of the long walls, which had been demolished at the end of the Peloponnesian War, and commanded the Athenian contingents at Nemea and Coronea; these two defeats, however, damaged his political stature, and he was replaced at the head of the state by Conon, whose victory at Cnidus had ended Sparta's dreams of naval empire.Thrasybulus largely faded from view for several years as Conon led the Athenian fleet to a series of victories, but in 392 BC Conon was imprisoned by the Persian satrap Tiribazus while attending a peace conference at Sardis; although released, he died in Cyprus without returning to Athens.  Thrasybulus, leading the faction that sought to reject the peace offer, regained his position atop Athenian politics.  In 389 BC, he led a force of triremes to levy tribute from cities around the Aegean and support Rhodes, where a democratic government was struggling against Sparta.  On this campaign, Thrasybulus relaid much of the framework for an Athenian empire on 5th century BC model; he captured Byzantium, imposed a duty on ships passing through the Hellespont, and collected tribute from many of the islands of the Aegean.  In 388 BC, as he led his fleet South through the Aegean, his soldiers ravaged the fields of Aspendus.  In retaliation, the Aspendians raided the...

Question: What did Thrasybulus capture?
Byzantium