eg ro , ▁and ▁almost ▁all ▁of ▁modern ▁Alban ia . ▁When ▁Du š an ▁died , ▁his ▁son ▁Stephen ▁U ro š ▁V ▁became ▁Emperor . ▁ ▁With ▁Turkish ▁inv aders ▁beginning ▁their ▁con quest ▁of ▁the ▁B alk ans ▁in ▁the ▁ 1 3 5 0 s , ▁a ▁major ▁conflict ▁en su ed ▁between ▁them ▁and ▁the ▁Ser bs , ▁the ▁first ▁major ▁battle ▁was ▁the ▁Battle ▁of ▁Mar its a ▁( 1 3 7 1 ), ▁in ▁which ▁the ▁Ser bs ▁were ▁defeated . ▁With ▁the ▁death ▁of ▁two ▁important ▁Ser b ▁leaders ▁in ▁the ▁battle , ▁and ▁with ▁the ▁death ▁of ▁Stephen ▁U ro š ▁that ▁same ▁year , ▁the ▁Ser bian ▁Empire ▁broke ▁up ▁into ▁several ▁small ▁Ser bian ▁domains . ▁These ▁states ▁were ▁ruled ▁by ▁fe ud al ▁l ords , ▁with ▁Z eta ▁controlled ▁by ▁the ▁Bal š ić ▁family , ▁Ra š ka , ▁Kos ovo ▁and ▁northern ▁Mac ed onia ▁held ▁by ▁the ▁B rank ović ▁family ▁and ▁Laz ar ▁H re bel jan ović ▁holding ▁today ' s ▁Central ▁Ser bia ▁and ▁a ▁portion ▁of ▁Kos ovo . ▁H re bel jan ović ▁was ▁subsequently ▁accepted ▁as ▁the ▁tit ular ▁leader ▁of ▁the ▁Ser bs ▁because ▁he ▁was ▁married ▁to ▁a ▁member ▁of ▁the ▁N eman ji ć ▁dynast y . ▁In ▁ 1 3 8 9 , ▁the ▁Ser bs ▁faced ▁the ▁Ott om ans ▁at ▁the ▁Battle ▁of ▁Kos ovo ▁on ▁the ▁plain ▁of ▁Kos ovo ▁Pol je , ▁near