, ▁leading ▁to ▁a ▁personal ▁union ▁in ▁ 1 5 6 9 . ▁ ▁S out he astern ▁Europe ▁ ▁Main ▁articles : ▁By z antine ▁Empire , ▁Second ▁Bulgar ian ▁Empire , ▁Ser bian ▁Grand ▁Princi p ality , ▁Princi p ality ▁of ▁Ar ban on , ▁Ban ate ▁of ▁Bos nia , ▁and ▁Kingdom ▁of ▁Cro atia ▁ ▁The ▁High ▁Middle ▁A ges ▁saw ▁the ▁height ▁and ▁decl ine ▁of ▁the ▁S lav ic ▁state ▁of ▁K ie van ▁Rus ' ▁and ▁emer gence ▁of ▁C um ania . ▁Later , ▁the ▁Mong ol ▁invasion ▁in ▁the ▁ 1 3 th ▁century ▁had ▁great ▁impact ▁on ▁the ▁east ▁of ▁Europe , ▁as ▁many ▁countries ▁of ▁the ▁region ▁were ▁inv aded , ▁pill aged , ▁conquer ed ▁and / or ▁v ass al ized . ▁ ▁During ▁the ▁first ▁half ▁of ▁this ▁period ▁( 1 1 8 5 ) ▁the ▁By z antine ▁Empire ▁domin ated ▁the ▁B alk ans , ▁and ▁under ▁the ▁Kom nen ian ▁em per ors ▁there ▁was ▁a ▁rev ival ▁of ▁prosper ity ▁and ▁urban ization ; ▁however , ▁their ▁dom ination ▁of ▁S out he astern ▁Europe ▁came ▁to ▁an ▁end ▁with ▁a ▁successful ▁V lach - B ul gar ian ▁re bell ion ▁in ▁ 1 1 8 5 , ▁and ▁hence for th ▁the ▁region ▁was ▁divided ▁between ▁the ▁By z ant ines ▁in ▁Greece , ▁some ▁parts ▁of ▁Mac ed onia , ▁and ▁Th race , ▁the ▁Bulg ari ans ▁in ▁Mo esia