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Model of the city of Sirmium
Model of the city of Sirmium | Photo:

Studying the history of the Roman Empire at school sometimes gives the impression that the centre of the most important events was in Italy, the regions of Western Europe, possibly Greece and then Constantinople. However, in the course of the history of the Empire, especially in the times of the late Empire, from the 3rd century CE, other cities played an important role, and the events taking place there influenced the entire country. One of such important cities, and rarely mentioned in history lessons, is Sirmium.

The city was located in the Balkans, in today’s Serbia, in the autonomous province of Vojvodina, on the Sava River, the longest right tributary of the Danube. Currently, the town of Sremska Mitrovica, with a population of around 40,000, is located in the area of ​​the ancient city. The Danube flows several dozen kilometres to the north, and Belgrade is located about 70 km to the east. Ten Roman emperors probably came from or around Sirmium. The favorable location on the border of the Empire on the Danube meant that the city became an important military camp and the headquarters of military operations carried out beyond the Danube. The large number of legions stationed also meant that the city was often a place of usurpation – the appointment of new emperors to the throne by the army. It was also the main residence of the emperors, who marked their reign by a large number of military campaigns. As a result of Diocletian’s administrative reform at the end of the 3rd century CE, the city became one of the four capitals of the Roman Empire.

Ruins of the palace imperial in Sirmium on the Sava.
Source:, CC BY-SA 3.0

History of the city until the 3rd century

In pre-Roman times, Sirmium was a Celtic settlement, and then an Illyrian one. During anti-Roman uprisings in Pannonia (Latin Bellum Pannonicum), around 14 BCE, the city was taken over by the governor of Ilyricum, Marcus Vinicius. After joining the Empire, the city developed rapidly, it became an important communication junction and economic center. By sailing the Sava River, on which the city was located, it was very easy to move from Italy to Singidunum (present-day Belgrade) and other eastern provinces. During the reign of the Flavian dynasty the city was granted the status of a colony of Roman citizens and was named Colonia Flavia Sirmium.

After the province of Pannonia was divided into two parts by Emperor Trajan, in CE 103, Sirmium probably became the capital of the eastern part – Pannonia Lower (Latin Pannonia Inferior). During the Marcomannian Wars (166-180 CE) Sirmium was the headquarters of Marcus Aurelius. It is probably here that the emperor wrote his philosophical work entitled Meditation. In Sirmium, Roman facilities were built such as the imperial palace, horse racing arena, mint, amphitheatre, theatre, public baths, temples, palaces, luxury villas and craft workshops.

From the 3rd century CE – the growing importance of Sirmium

From 235 CE, which is also considered the beginning of the crisis of the Empire, events were taking place in the Sirmium that were important to the fate of the entire Empire. It is during this time, from 235 CE until 284 CE reigned the so-called soldier emperors, often called Augustus in Sirmium. Some of them also came from its vicinity, enlisting in the army at an early age, climbing higher and higher in the hierarchy, eventually becoming emperors. As early as the fall of 235 CE Sirmium was the headquarters of Maximinus Thrax, fighting the Sarmatians and the Dacians. In 249 CE The Danubian legions chose as emperor Decius Trajan, who came from the vicinity of Sirmium, who appointed his sons: Herennius and Hostilian as his co-rulers. Decius and Herennius died in June 251 CE. under Abrittus in the fight against the Goths. Decius’s second son died a few months later as a result of an epidemic. Emperor Claudius II the Gothic was associated with Sirmium throughout his life. He was certainly from Illyricum, perhaps also from the vicinity of the city on the Sava River, coming from quite low social values. Claudius II defeated the Goths in the great battle of Naissus in 269 CE, which he owes the nickname “Gothic”. However, the victorious emperor died shortly after, in early 270 CE. – in Sirmium, and a few months later his brother and co-ruler Quintillus committed suicide.

After Claudius II in the legionary camp in Sirmium, Aurelian was proclaimed emperor – one of the most outstanding emperors of the 3rd century CE. Like his predecessor, he probably came from the vicinity of Sirmium. His reign (270 – 275 CE) was a series of successes, thanks to which the Empire slowly began to recover from the crisis. Another emperor associated with Sirmium was Probus (he ruled in the years 276 – 282 CE), appointed emperor in the eastern provinces, but he was born in Sirmium itself. The circumstances of his death were related to his hometown. Probus, trying to restore discipline in the army, forced legionaries to perform heavy physical work, which resulted in a decline in his popularity. The soldiers forced to dig the canals in Sirmium revolted, and the Emperor himself fell victim. According to some hypotheses, the perpetrator of the rebellion could also be another emperor – Carus.

In 293 CE Emperor Diocletian created a new system of government – tetrarchy, choosing a second co-ruler – with the title Augustus, and two lower – Caesars. Sirmium became one of the four capitals of the Roman Empire and the seat of Galerius – Caesar, ruling the Balkan provinces and defending them against the barbarians across the Danube.

In 296 CE as a result of a new administrative division established by Diocletian, Sirmium became the capital of a new province – Pannonia Secunda, and of a higher organizational unit – the Diocese of Pannonia.

Augustus and the co-ruler of the Empire together with Diocletian – Maximian Herculius, probably from the lower social classes, came from the vicinity of Sirmium.

Further history of the city

In the years 318 – 379 CE Sirmium was the capital of the Prefecture of Illyria, an administrative division above the diocese and provinces. At the beginning of the 4th century CE, the city on the Sava River was for a time the residence of Constantine the Great. Probably moved in the 3rd century CE the centre of gravity of important events in the Roman Empire to Sirmium as well as to Nicomedia in Bithynia gave Constantine the idea of ​​building a new capital in Constantinople. However, Sirmium itself was not suitable for the new capital due to its proximity to the external border.

In the city and military camp on the Sava River, Emperor Constantius II was born and associated with it. During his reign, in 350 CE Sirmium, however, was the centre of usurpation of Wetronian, who, however, rather quickly surrendered to Constantius. In 351 CE It was in Sirmium that Constantius II appointed his cousin Gallus as co-ruler and Caesar, and it was his headquarters during his victorious civil war with Magnentius, as well as his fights with the Sarmatian tribes from across the Danube. Despite Sirmium’s ties with Constantius II during the civil war with Julian the Apostate, the city and the military garrison quite easily in 361 CE. passed over to the latter, only to change fronts in a moment and recognize Constantius again. The second shift of front did nothing, however, as the current emperor died and the only ruler of the Empire was Julian the Apostate.

In 364 CE the two co-rulers Valentinian I and Valens in Sirmium divided responsibility for the areas of the Empire – Valens east, Valentinian – west. It was a harbinger of the events of the future when 30 years later the final division of the Empire into the Western and Eastern Empire will take place. After the death of Valentinian I to 378 CE Sirmium was the residence of a minor Valentinian II, and his older son, Emperor Gratian, was born in a city on the Sava River. In 379 CE in Sirmium, the emperor of Theodosius the Great was declared. He was chosen by Gratian as co-ruler in the face of the death of Valens at Adrianople and the minority of Valentinian II.


Sirmium was an important centre of Christianity in the Balkans. The seat of the bishopric was here, the first bishop known by name was Irenaeus, murdered during the Diocletian persecution. City in the 4th century CE became a major centre of Arianism. Five synods were held here in 347, 351, 357, 358, 375, or 378 CE. The third one contained a temporary compromise with the Nicene faith, but the others recognized the superiority of the Arian doctrine.


At the end of the 4th century CE, the city was conquered by the Goths but returned fairly quickly to the Eastern Roman Empire. In 441 CE was conquered by Huns, later it was owned by the Gepids (it was even the capital of their country), the Ostrogoths of Theodoric the Great, the Lombards and the Avars. In 567 CE it was again conquered by the Byzantine Empire. The city certainly had a strategic and historical significance for the heirs of the Romans.

In 582 CE the city was again conquered by the Avars and this time destroyed. Probably the demolition of the ancient city, the former residence of many emperors and a symbol resembling the Roman rule in Pannonia, was to prevent their return to the Eastern Roman Empire. The conquest of Sirmium had a decisive influence on the further history of the Balkans, the Byzantines did not return to the western Danube basin, and the Avars and Slavs invaded the Balkans.

Author: Eligiusz Idczak (translated from Polish: Jakub Jasiński)
  • Aleksander Krawczuk, Poczet Cesarzy Rzymskich. Dominat. Warszawa 1991.
  • Bora Čekerinac, Sirmium - Sremska Mitrovica. Illustrated chronology from prehistory to the beginning of the 21st century. Sremska Mitrovica 2011.
  • Michael Durst, Sirmium, Freiburg 2000.
  • Walter Pohl, Die Awaren. Ein Steppenvolk in Mitteleuropa 567–822 n. Chr, Monachium 1988.

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