sentences:  The success of the conversion of the Bulgarians facilitated the conversion of other East Slavic peoples, most notably the Rus', predecessors of Belarusians, Russians, and Ukrainians.By the beginning of the 11th century most of the Slavic world, including, Bulgaria, Serbia, and Russia had converted to Orthodox Christianity.Bulgaria's Church was officially recognized as a Patriarchate by Constantinople in 927, Serbia's in 1346, and Russia's in 1589.