Empire, serving as its capital during the Tetrarchy. Contemporary Serbia comprises the classical regions of Moesia, Pannonia, parts of Dalmatia, Dacia and Macedonia. The chief towns of Upper Moesia in the Principate were: Naissus (modern Niš), Viminacium (sometimes called municipium Aelium; modern Kostolac), Singidunum (modern Belgrade), Remesiana (modern Bela Palanka) Many Roman noblemen and statesmen were born in present-day Serbia, including 17 or 18 Roman Emperors (Vetranio wasn't universally recognized as an emperor, but was proclaimed a caesar). Byzantine period The Byzantine era in the history Serbia refers to three distinctive periods. The territory of later Serbia was under control of the Eastern Roman Empire up to the beginning of the 7th century. During that period, emperor Justinian I (527–565) oversaw reinforcement of defensive structures in the region, and founded the city of Justiniana Prima, today a Cultural Heritage of Serbia-listed archeological site (Archaeological Sites of Exceptional Importance). In 535, the city became center of the Archbishopric of Justiniana Prima, that had metropolitan jurisdiction over all provinces of the Diocese of Dacia. At the beginning of the 7th century, region was invaded by Avars and Slavs, thus ending the Byzantine rule. From that time, and up to the middle of the 10th century, the region was controlled by the newly created Slavic state - the early medieval Principality of Serbia. In 971–976, Byzantine rule was briefly restored, and Catepanate of Ras was established, but it was short lived. Only after 1018, the territory of Serbia came under the Byzantine rule, and it was included into two themata: the Theme of Serbia and the Theme of Sirmium, that existed until 1071. Arrival of the Slavs The Byzantines broadly grouped the numerous Slav tribes into two groups: the Sklavenoi and Antes. Apparently, the Sklavenoi group were based along the middle Danube, whereas the Antes were at the lower Danube, in Scythia Minor. Some, such as Bulgarian scholar Zlatarsky, suggest that the first group settled the western Balkans, whilst offshoots of the Antes settled the eastern regions (roughly speaking). From the Danube, they commenced raiding the Byzantine Empire from the 520s, on an annual basis. They spread about destruction, taking loot and herds of cattle, seizing prisoners and taking fortresses. Often, the Byzantine Empire was stretched defending its rich Asian provinces from Arabs, Persians and Turks. This meant that even numerically small, disorganised early Slavic raids were capable of causing much disruption, but