▁g arr isons ▁to ▁the ▁south ▁of ▁the ▁B alk an ▁mountains . ▁The ▁Bulgar ian ▁tact ics ▁included ▁quick ▁assault s ▁and ▁has te ▁movement ▁and ▁the ▁By z ant ines ▁were ▁unable ▁to ▁charge ▁them . ▁ ▁In ▁order ▁to ▁change ▁that ▁situation , ▁the ▁By z antine ▁Emperor , ▁Isaac ▁II ▁Angel os , ▁decided ▁to ▁move ▁the ▁military ▁actions ▁to ▁northern ▁Bulg aria ▁and ▁strike ▁directly ▁to ▁the ▁re bel ' s ▁heart lands ▁around ▁T arn ovo . ▁ ▁The ▁sie ge ▁ ▁In ▁the ▁late ▁aut umn ▁of ▁ 1 1 8 6 , ▁the ▁By z antine ▁army ▁march ed ▁north wards ▁through ▁S red ets ▁( S of ia ). ▁The ▁campaign ▁was ▁planned ▁to ▁surprise ▁the ▁Bulg ari ans . ▁However , ▁the ▁har sh ▁weather ▁conditions ▁and ▁the ▁early ▁winter ▁post pon ed ▁the ▁By z ant ines ▁and ▁their ▁army ▁had ▁to ▁stay ▁in ▁S red ets ▁during ▁the ▁whole ▁winter . ▁ ▁In ▁the ▁spring ▁of ▁the ▁following ▁year , ▁the ▁campaign ▁was ▁res umed , ▁but ▁the ▁element ▁of ▁surprise ▁was ▁gone ▁and ▁the ▁Bulg ari ans ▁had ▁taken ▁measures ▁to ▁bar ▁the ▁way ▁to ▁their ▁capital ▁T arn ovo . ▁Instead ▁the ▁By z ant ines ▁bes ie ged ▁the ▁strong ▁for tr ess ▁of ▁Love ch . ▁The ▁sie ge ▁last ed ▁for ▁three ▁month ▁and ▁was ▁a ▁complete ▁failure . ▁Their ▁only ▁success ▁was ▁the ▁capture ▁of ▁As en ' s ▁wife , ▁but ▁Isaac ▁was ▁forced