Sirmium: Roman city and river port in Pannonia. The city became an imperial residence and is identical to modern Sremska Mitrovica.
The early history of Roman Sirmium is poorly documented, but it is certain that by the age of the emperor Vespasian (r.69-79), the city had received the rank of colonia.note[CIL 3.4991.] Inscriptions refer to the normal civil officials, like duumviri and quaestores. It has been assumed that the Ninth Legion Hispana was at Sirmium at the beginning of our era, while an inscription (shown below) appears to document the stay of the Second Legion Adiutrix at Sirmium during the reign of Domitian.Most archaeological monuments belong to the second century and later. The emperors Trajan (who in 103 made Sirmium the capital of the province of Lower Pannonia) used the city as base for his first Dacian War. Later, Marcus Aurelius resided in Sirmium when he waged war against the northern tribes. It was also the scene of the trial of Herod Atticus.note[Philostratus, Lives of the Sophists 560ff.]
Maximinus Thrax was in the city, preparing for an attack on the Germanic tribes, when in 238 civil war broke out.note[Herodian, Roman History 7.2.9.] Tombstones of legionaries prove how important the city was as base for the Roman army. There is evidence for the presence of soldiers from II Adiutrix, XIII Gemina, I Minervia, and VIII Augusta. Subunits of the two last-mentioned units, both from the Rhine army, were probably in Sirmium until c.260.
When in 318 the Roman Empire was divided into four regions, Sirmium became the capital of the Prefecture of Illyricum. Three legions, IIII Flavia, V Iovia and VI Herculia, protected the city against Germanic tribes in the north. Their bases were at Singidunum, Castellum Onagrinum, and Teutoburgium.
In Late Antiquity, the Pannonian provinces were first conquered by the Huns, who took Sirmium in 441. When this tribal federation fell apart after the death of king Atilla, the Ostrogoths remained in control of Pannonia, but when the Byzantine emperor Justinian suggested them to go to Italy, they left the region. For a while, the Gepids were the city's masters, but after 567, the city returned to the Empire again, only to be besieged by the Avars. A silent witness of this war is a rooftile, dated to 582, with a prayer inscribed on it.
Christ, our Lord,
help our city halt the Avars.
Protect the Roman Empire,
and he who was written this.
It did not help: the city was sacked. Yet, it survived, and there was still a military district called "Sirmion" in the tenth-century Byzantine Empire.