of Pannonia in the north and Dalmatia in the south. The date of the division is unknown, most certainly after AD 20 but before AD 50. The proximity of dangerous barbarian tribes (Quadi, Marcomanni) necessitated the presence of a large number of troops (seven legions in later times), and numerous fortresses were built on the bank of the Danube. Some time between the years 102 and 107, between the first and second Dacian wars, Trajan divided the province into Pannonia Superior (western part with the capital Carnuntum), and Pannonia Inferior (eastern part with the capitals in Aquincum and Sirmium). According to Ptolemy, these divisions were separated by a line drawn from Arrabona in the north to Servitium in the south; later, the boundary was placed further east. The whole country was sometimes called the Pannonias (Pannoniae). Pannonia Superior was under the consular legate, who had formerly administered the single province, and had three legions under his control. Pannonia Inferior was at first under a praetorian legate with a single legion as the garrison; after Marcus Aurelius, it was under a consular legate, but still with only one legion. The frontier on the Danube was protected by the establishment of the two colonies Aelia Mursia and Aelia Aquincum by Hadrian. Under Diocletian, a fourfold division of the country was made: Pannonia Prima in the northwest, with its capital in Savaria / Sabaria, it included Upper Pannonia and the major part of Central Pannonia between the Raba and Drava, Pannonia Valeria in the northeast, with its capital in Sopianae, it comprised the remainder of Central Pannonia between the Raba, Drava and Danube, Pannonia Savia in the southwest, with its capital in Siscia, Pannonia Secunda in the southeast, with its capital in Sirmium Diocletian also moved parts of today's Slovenia out of Pannonia and incorporated them in Noricum. In 324 AD, Constantine I enlarged the borders of Roman Pannonia to the east, annexing the plains of what is now eastern Hungary, northern Serbia and western Romania up to the limes that he created: the Devil's Dykes. In the 4th-5th century, one of the dioceses of the Roman Empire was known as the Diocese of Pannonia. It had its capital in Sirmium and included all four provinces that were formed from historical Pannonia, as well as the provinces of Dalmatia, Noricum Mediterraneum and Noricum Ripense. In the 4th century, the Romans (especially under Valentinian