 Organised prehistoric cultures began developing on current Bulgarian lands during the Neolithic period . Its ancient history saw the presence of the Thracians , Greeks and Romans . The emergence of a unified Bulgarian state dates back to the establishment of the First Bulgarian Empire in 681 AD , which dominated most of the Balkans and functioned as a cultural hub for Slavs during the Middle Ages . With the downfall of the Second Bulgarian Empire in 1396 , its territories came under Ottoman rule for nearly five centuries . The Russo @-@ Turkish War of 1877 – 78 led to the formation of the Third Bulgarian State . The following years saw several conflicts with its neighbours , which prompted Bulgaria to align with Germany in both world wars . In 1946 it became a one @-@ party socialist state as part of the Soviet @-@ led Eastern Bloc . In December 1989 the ruling Communist Party allowed multi @-@ party elections , which subsequently led to Bulgaria 's transition into a democracy and a market @-@ based economy . 
