 The name "Africa," which was originally used by the Romans to refer to present-day Tunisia, only began to be stretched to encompass a larger area when the provinces of Tripolitania, Numidia and Mauretania Caesariensis were subdued to the Diocesis of Africa, following the administrative restructuring of Diocletian.Later, when Justinian I reconquered lands of the former West Roman Empire, all the regions from the Chelif River to the Gulf of Sidra were annexed to the Byzantine Empire as the "Exarchate of Africa".During the Middle Ages, as the Europeans increased their knowledge and awareness of the size of the African continent, they progressively extended the name of Africa to the rest of the continent.