In ancient times Erzurum existed under the name of Karin. During the reigns of the Artaxiad and Arsacid kings of Armenia, Karin served as the capital of the region of Karin.

After the partition of Armenia between the Roman Empire and Sassanid Persia in 387, the city passed into the hands of the Romans. They fortified the city and renamed it Theodosiopolis, after Emperor Theodosius I.

As the chief military stronghold along the eastern border of the empire, Theodosiopolis held a highly important strategic location and was fiercely contested in wars between the Byzantines and Persians. Emperors Anastasius I and Justinian I both refortified the city and built new defenses during their reigns.

Erzurum is a city in eastern Anatolia, Turkey. The name "Erzurum" derives from "Arz-e Rum." The town was known in Roman and subsequently Byzantine times as Theodosiopolis, acquiring its present name after its conquest by the Seljuk Turks following the Battle of Manzikert in 1071.