▁ ▁In ▁the ▁ 4 th - 5 th ▁century , ▁one ▁of ▁the ▁dioc eses ▁of ▁the ▁Roman ▁Empire ▁was ▁known ▁as ▁the ▁Dioc ese ▁of ▁P ann onia . ▁It ▁had ▁its ▁capital ▁in ▁S irm ium ▁and ▁included ▁all ▁four ▁provinces ▁that ▁were ▁formed ▁from ▁historical ▁P ann onia , ▁as ▁well ▁as ▁the ▁provinces ▁of ▁Dal mat ia , ▁Nor icum ▁Mediter rane um ▁and ▁Nor icum ▁R ip ense . ▁ ▁Post - R oman ▁ ▁During ▁the ▁M igr ations ▁Period ▁in ▁the ▁ 5 th ▁century , ▁some ▁parts ▁of ▁P ann onia ▁was ▁c eded ▁to ▁the ▁H uns ▁in ▁ 4 3 3 ▁by ▁F la vi us ▁A et ius , ▁the ▁mag ister ▁milit um ▁of ▁the ▁Western ▁Roman ▁Empire . ▁After ▁the ▁collapse ▁of ▁the ▁H unn ic ▁emp ire ▁in ▁ 4 5 4 , ▁large ▁numbers ▁of ▁Ost rog oth s ▁were ▁settled ▁by ▁Mar cian ▁ ▁in ▁the ▁province ▁as ▁fo eder ati . ▁The ▁Eastern ▁Roman ▁Empire ▁controlled ▁it ▁for ▁a ▁time ▁in ▁the ▁ 6 th ▁century , ▁and ▁a ▁By z antine ▁province ▁of ▁P ann onia ▁with ▁its ▁capital ▁at ▁S irm ium ▁was ▁tempor arily ▁restored , ▁but ▁it ▁included ▁only ▁a ▁small ▁sout he astern ▁part ▁of ▁historical ▁P ann onia . ▁ ▁After wards , ▁it ▁was ▁again ▁inv aded ▁by ▁the ▁Av ars ▁in ▁the ▁ 5 6 0 s , ▁the ▁S lav s , ▁who ▁first ▁settled ▁c