The trireme was an ancient oar-powered warship, first built by Athens at the time of Themistocles (524-459BC) but rapidly copied by other Greek city-states. It was developed from the “pentekonter”, a large Greek war galley, by installing three banks of oars per side with the oarsmen arranged one above the other; thus creating a vessel larger and speedier than previously possible. Initially, the trireme (or “trier”) was manned by about 170 rowers (Usually thetes – poor freeman who rowed for payment), 20 or so sailors and officers and about ten marines. The captain – trierar or trierarch – was responsible for the ship at all times; providing the money for its repairs and maintenance as well as running costs.
For longer voyages, auxiliary sails were available; a mainsail amidships and a smaller sail near the prow (front). The prow and fore part of the ship were strengthened to allow a large bronze- or iron-clad ram which was used to either slice into an enemy ship from the side, or snap its oars by running alongside. Steering was by large steering oars near the stern, one on each side of the vessel. This was the predominant warship in the Mediterranean for the next few centuries.
In 146BC the Romans, at war with Carthage, began construction of a large fleet of warships based on the Greek design, but adapted to suit Roman fighting techniques. The most innovative feature of the Roman trireme was a strong boarding plank attached to a mast on the foredeck and mounted on a swivel. This plank was dropped onto the deck of the enemy where it was held fast by an iron spike on the end of the plank. The Romans could then board and use their superior hand-to-hand battle skills to subdue the enemy.
Reference: “Dictionary of Ship Types” (Dudszus & Henriot)