By the time ancient Rome rose to power, the trireme had lost its position as the dominant war vessel. Dionysius the Elder, the aristocratic ruler of Sicily, built a navy of about 300 vessels that featured quadriremes and quinqueremes. Historians doubt that these ships had four and five banks of oarsmen, as their names suggest. Instead, it is believed four to five men worked together to row each oar. These ships often carried 100 fighting men and either a stone-throwing catapult to attack port towns or bowed catapults that fired darts or stones. The Roman navy also came to rely on Liburnian galleys, small, two-level ships known for their speed.
Long banks of oars propelled the Roman warship swiftly through the water and into battle. Roman cargo ships featured the same distinctive square sails, but warships often had additional protective coverings to shield them from fire and missiles.
The navy protected Roman merchant ships from enemies and pirates. The sophisticated merchant ships were large, high-sided vessels with two or three masts that flew square sails. Many measured 500 tons, and historians theorize that special ships used to transport Egyptian grain to Roman territories exceeded 1,000 tons. No examples of the grain transports have been recovered, however. Roman galleys and merchant ships dominated the Mediterranean until the Western Empire broke up in the 5th century AD.