Fossatum Africae ("African ditch") is one or more linear defensive structures (sometimes called limes) claimed to extend over or more in northern Africa constructed during the Roman Empire to defend and control the southern borders of the Empire in Africa. It is considered to be part of the greater frontier system in Roman Africa. It is considered to have many similarities of construction to Hadrian's Wall, one of the northern borders of the Empire in Britain. History The Fossa regia was the first frontier line to be built in Roman Africa, used to initially divide the Berber kingdom of Numidia from the territory of Carthage that was conquered by the Romans in the second century, but this is considered to be independent of the Fossatum Africae. There is only a single mention of the Fossatum (as such) in historical literature prior to the 20th century. This occurs in a letter written by the co-emperors Honorius and Theodosius II to Gaudentius, the vicarius Africae, in 409, and preserved in the Codex Theodosianus. Noting that the fossatum had been established by the "ancients", the emperors warned the Roman citizens of Africa that if they did not maintain the limes and fossatum then the job (with associated land rights and other advantages) would be given to friendly barbarian tribes. Consequently, it is not known with certainty when the Fossatum was constructed. Of course, a structure of this size would be the work of centuries, and the archaeological excavation of the many forts and towns along its route has yielded many dates from the reign of Hadrian in the 2nd century to Constantine in the 4th century. Current opinion has not advanced since the discussion by Baradez in 1949, who concluded that construction probably began after the first visit of Hadrian to Africa in 122 (and before or after his second visit in 128). This conclusion is based on the similarities with Hadrian's Wall in Britain and with what is known about Hadrian's concern to protect the Empire. Baradez also postulated a pulse of construction during the reign of Gordian III in the 3rd century, and finally abandonment of the Fossatum in 430–440 after the Vandal invasion. Having been built in an arid region of strong winds and blowing sand, the Fossatum quickly eroded and only traces remain. During the Middle Ages, Arab nomads of the Banu Hilal occupied much of the area and