 Tarnovo was captured by the Ottomans after a three @-@ month siege in 1393 . After the Battle of Nicopolis in 1396 brought about the fall of the Vidin Tsardom , the Ottomans conquered all Bulgarian lands south of the Danube . The nobility was eliminated and the peasantry was enserfed to Ottoman masters , with much of the educated clergy fleeing to other countries . Under the Ottoman system , Christians were considered an inferior class of people . Thus , Bulgarians , like other Christians , were subjected to heavy taxes and a small portion of the Bulgarian populace experienced partial or complete Islamisation , and their culture was suppressed . Ottoman authorities established the Rum Millet , a religious administrative community which governed all Orthodox Christians regardless of their ethnicity . Most of the local population gradually lost its distinct national consciousness , identifying as Christians . However , the clergy remaining in some isolated monasteries kept it alive , and that helped it to survive as in some rural , remote areas , as well as in the militant Catholic community in the northwestern part of the country . 
