As the Western Roman Empire fell to Germanic tribes and its own internal problems, the Roman Empire in the east, called the Byzantine Empire, flourished.
The Byzantine navy transported soldiers and supplies to help recover the Western Empire. The navy relied on fast galleys called dromons, or racers, to accompany and protect the supply ships. Early dromons had a single bank of oarsmen, but Byzantine shipbuilders later incorporated a second level for oarsmen.
For cargo transport, the Byzantines usually commandeered ordinary merchantmen as transport ships or supply ships. These appear to have been mostly sailing vessels, rather than oared. The Byzantines and Arabs also employed horse-transports, which were either sailing ships or galleys, the latter certainly modified to accommodate the horses.