They were the first civilization to create the bireme. The bireme eventually evolved into the trireme. A few Genoese freight contracts of the mid-13th century record charters for bireme galleys. Early bireme galleys escorted merchant ships but were rarely used to carry goods. A bireme is an ancient oared warship (galley) with two decks of oars. The bireme was twice the triaconter's length and height, and thus employed 120 rowers. A "monoreme" has one bank of oars, a "bireme" two, and a "trireme" three.