1 1 th ▁century , ▁" R a š ka " ▁separated ▁from ▁it ▁and ▁replaced ▁it ▁as ▁the ▁most ▁powerful ▁Ser bian ▁state . ▁Prince ▁Stefan ▁N eman ja ▁( r . ▁ 1 1 6 9 – 9 6 ) ▁conquer ed ▁the ▁neighbour ing ▁territ ories ▁of ▁Kos ovo , ▁D uk l ja ▁and ▁Zach l um ia . ▁The ▁N eman ji ć ▁dynast y ▁ruled ▁over ▁Ser bia ▁until ▁the ▁ 1 4 th ▁century . ▁N eman ja ' s ▁older ▁son , ▁Stefan ▁N eman ji ć , ▁became ▁Ser bia ' s ▁first ▁recognized ▁king , ▁while ▁his ▁younger ▁son , ▁R ast ko , ▁founded ▁the ▁Ser bian ▁Orth odox ▁Church ▁in ▁the ▁year ▁ 1 2 1 9 , ▁and ▁became ▁known ▁as ▁Saint ▁S ava ▁after ▁his ▁death . ▁ ▁Over ▁the ▁next ▁ 1 4 0 ▁years , ▁Ser bia ▁expanded ▁its ▁borders , ▁from ▁numerous ▁smaller ▁principal ities , ▁reaching ▁to ▁a ▁un ified ▁Ser bian ▁Empire . ▁Its ▁cultural ▁model ▁remained ▁By z antine , ▁despite ▁political ▁amb itions ▁directed ▁against ▁the ▁emp ire . ▁The ▁medieval ▁power ▁and ▁influence ▁of ▁Ser bia ▁cul min ated ▁in ▁the ▁reign ▁of ▁Stefan ▁Du š an , ▁who ▁ruled ▁the ▁state ▁from ▁ 1 3 3 1 ▁until ▁his ▁death ▁in ▁ 1 3 5 5 . ▁R uling ▁as ▁Emperor ▁from ▁ 1 3 4 6 , ▁his ▁territory ▁included ▁Mac ed onia , ▁northern ▁Greece , ▁Mont en