cultural and political expansion into the region, from the 5th up to the 2nd century BC. The Celtic tribe of Scordisci settled throughout the area in the 3rd century BC. It formed a tribal state, building several fortifications, including their capital at Singidunum (present-day Belgrade) and Naissos (present-day Niš). The Romans conquered much of the territory in the 2nd century BC. In 167 BC, the Roman province of Illyricum was established; the remainder was conquered around 75 BC, forming the Roman province of Moesia Superior; the modern-day Srem region was conquered in 9 BC; and Bačka and Banat in 106 AD after the Dacian Wars. As a result of this, contemporary Serbia extends fully or partially over several former Roman provinces, including Moesia, Pannonia, Praevalitana, Dalmatia, Dacia, and Macedonia. The chief towns of Upper Moesia (and broader) were: Singidunum (Belgrade), Viminacium (now Old Kostolac), Remesiana (now Bela Palanka), Naissos (Niš), and Sirmium (now Sremska Mitrovica), the latter of which served as a Roman capital during the Tetrarchy. Seventeen Roman Emperors were born in the area of modern-day Serbia, second only to contemporary Italy. The most famous of these was Constantine the Great, the first Christian Emperor, who issued an edict ordering religious tolerance throughout the Empire. When the Roman Empire was divided in 395, most of Serbia remained under the Eastern Roman Empire. At the same time, its northwestern parts were included in the Western Roman Empire. By the 6th century, South Slavs migrated into the European provinces of the Byzantine Empire in large numbers. They merged with the local Romanised population that was gradually assimilated. Middle Ages White Serbs, an early Slavic tribe from White Serbia eventually settled in an area between the Sava river and the Dinaric Alps. By the beginning of the 9th century, Serbia achieved a level of statehood. Christianization of Serbia was a gradual process, finalized by the middle of the 9th century. In the mid-10th-century, the Serbian state stretched between the Adriatic Sea, the Neretva, the Sava, the Morava, and Skadar. During the 11th and 12th century, Serbian state frequently fought with the neighbouring Byzantine Empire. Between 1166 and 1371, Serbia was ruled by the Nemanjić dynasty (whose legacy is especially cherished), under whom the state was elevated to a kingdom in 1217, and an empire in 1346, under Stefan Dušan. Serbian Orthodox Church was organized as an autocephalous archbishopric in 1219, through the