Precise definitions of, e.g., a liburna, a mainstay of Roman fleets, or Constantine I's triaconters
[AD 324], which sounded the trireme's death knell, float in the air.
Philip was in a position to 'practise piracy', because he had developed a fleet of triaconters and penteconters, which were fast under oar and could attack the small merchantmen of the time.(13) Athens and Philip being at war raided each other's shipping in the northern Aegean.
Moreover, he enjoyed in that area the alliance of Perinthus and Byzantium, was negotiating with Chios, Rhodes and their allies (FGrH 115 [Theopompus] F 164), and had himself built penteconters and triaconters which were ideal for raiding merchant-ships, or as the Athenians put it for 'piracy' (Just.