Pannonia Inferior in the context of "Sarmatia"

The territory of the modern state of Serbia was part of the Roman Empire and later the Eastern Roman Empire. In particular, the region of Central Serbia was under Roman rule for about 800 years (with interruptions), starting from the 1st century BC, interrupted by the arrival of the Slavs into the Balkans during the 6th century, but continued after fall of the First Bulgarian Empire in the early 11th century and permanently ended with the rise of the Second Bulgarian Empire in the late 12th century. The territories were administratively divided into the provinces of Moesia (later Moesia Superior), Pannonia (later Pannonia Inferior) and Dardania. Moesia Superior roughly corresponds to modern Serbia proper; Pannonia Inferior included the eastern part of Serbia proper; Dardania included the western part of Serbia proper. After its reconquest from the Bulgarians by Emperor Basil II in 1018, it was reorganized into the Theme of Bulgaria.

The Danube River influenced the extension of the Roman Empire; its confluents, such as Sava and Morava, affected the growth of frontier fortresses and towns. Many authors and explorers wrote about traces of the Roman Empire on the Danube coast. One of the localities, Felix Romuliana, was ranked on the list of cultural heritage of UNESCO in July 2007.

Sirmium was a city in the Roman province of Pannonia, located on the Sava river, on the site of modern Sremska Mitrovica in the Vojvodina autonomous province of Serbia. First mentioned in the 4th century BC and originally inhabited by Illyrians and Celts, it was conquered by the Romans in the 1st century BC and subsequently became the capital of the Roman province of Pannonia Inferior. In 293 AD, Sirmium was proclaimed one of the four capitals of the Roman Empire. It was also the capital of the Praetorian prefecture of Illyricum and of Pannonia Secunda. The site is protected as an archaeological Site of Exceptional Importance. The modern region of Syrmia (Srem or Srijem) was named after the city.

Sirmium purportedly had 100,000 inhabitants and was one of the largest cities of its time. Colin McEvedy, whose estimates for ancient cities are much lower than the general consensus, put the population at only 7,000, based on the size of the archaeological site. The amount of grain imported between 1 AD and 400 AD was enough to feed 700,000 to 1 million people.

The Danubian provinces of the Roman Empire were the provinces of the Lower Danube, within a geographical area encompassing the middle and lower Danube basins, the Eastern Alps, the Dinarides, and the Balkans. They include Noricum, Dacia (Trajana and Aureliana), the northern part of Dalmatia, Moesia (Inferior and Superior), Scythia Minor, and Pannonia (Superior and Inferior). The Danube defined the region to the north, with the Carpathian Mountains to the north and east. These provinces were important to the Imperial economy as mining regions, and their general significance in the Empire of the 3rd century is indicated by the emperors who came from the region.

The Roman presence in the region can be described as having four phases from Augustus to Hadrian: military conquest under Augustus, and consequent military actions; the establishment of military bases along roads and river crossings under Claudius; the establishment of camps along the river for stationing legions and auxiliaries carried out by the Flavian dynasty and Trajan; and further expansion into Dacia north of the Danube. Hadrian's approach was to defend and maintain, a policy that remained more or less in effect until the latter 4th century, when Roman control disintegrated. The pattern of Roman settlement after the time of Hadrian became standard: a fort (castra), a military town (canabae) associated with it, and a town (municipium) developing two or three miles away.