Following the collapse of the Roman Empire in the 5th century AD, Singidunum was governed by various sovereigns from different medieval states. For the Byzantine Empire, Belgrade was an important border fortress which hindered barbaric invasions aimed at its territories in the Balkans. Byzantine historian Procopius claims that Iustinian rebuilt Belgrade. During the 6th century, Slavs and Avars appeared before the gates of Belgrade. With the Great migrations and barbaric conquests, the name Singidunum became obsolete. The process of permanent settlement of Slavs occured in the 7th century. After a period of Bulgarian reign in Belgrade during the 9th and 10th centuries, Belgrade had once again become an important Byzantine fortress in 1018. However, after the demise of Samuel’s medieval state, The Byzantine Empire had become a neighbor of the Kingdom of Hungary, that had also intended to conquer the area towards Srem. A period ensued of the constan fighting for dominance over Belgrade. A lengthier time of peace was brought forth by emperor Manuel I Komnenos in 1167 after a peace treaty was signed following his victory over Hungarian forces. During his military campaigns he stayed at Belgrade on multiple occasions. For Belgrade, the reign of Manuel I Komnenos signified the period of the final rise of The Byzantine Empire in the fortress. In the final decades of the 12th century, the Byzantines had gradually started losing control over Belgrade, which was followed by a period of crusades during which Belgrade was visited by Friedrich II Barbarossa and his crusaders.
Translated by Filip Šuica