Galley, early seagoing warship, propelled by oars, sometimes with auxiliary sails. The galleys that made up the ancient Greek and Roman navies were classified according to the number of banks of oars on each side: uniremes (1 bank), biremes (2 banks), and triremes (3 banks). There were usually about 25 oars per bank. The oars were 40–50 ft (12–15 m) long and as many as 7 slaves were required to work each oar. Galleys were long and narrow. Though fast, they were difficult to handle in rough seas. They were equipped with catapults and carried archers and soldiers who would board an enemy ship that had been rammed. Galleys were used in the Mediterranean and other seas until the late 17th century.