Battle of the Osam

In 569, the Lombard king Alboin, accompanied by a strong military force composed of his own people, Gepids and Pannonian Bulgars, conquered substantial territories in northern Italy, including Lombardy, Etruria and Liguria. As a result of these conquests, settlements of various peoples, including Bulgars, were established in these areas. This marked the beginning of Bulgar migration to Italy, which would later grow in scale.

While some Bulgars left their second homeland in Pannonia and settled in Italy, others continued to live in Pannonia and actively participated in the Avar Khaganate's campaigns against the Byzantine Empire, usually alongside the Slavs. One important event was the Avar khagan's major campaign of 584, when a large number of Byzantine captives, about 270,000 men and women, were settled between the Drava and Sava rivers near the khaganate's Bulgar populations. In 597, a detachment of 1,000 Bulgar warriors clashed with a Byzantine army near the mouth of the Osam River.

The following year, under Khagan Bayan, the Bulgars captured Singidunum in response to Byzantine actions.