A bireme is a ship probably invente by the Phoenicians whose best known use was as an ancient greek naval ship that was 80 feet (24 metres) long with a maximum beam length of around 10 feet (3 metres). It was modified from unireme (a ship that had only one set of oars on each side) but the bireme had two sets of oars on each side, hence the name. It also had a large square sail. This ship was also used by the Romans frequently and were used during the second of Caesar's invasions of Britain. It evolved into the trireme. Often there would be a group of marines and a unit commandant (the commandant was given a tent on the open deck).