Bulgaria changed systems of government.
Bulgaria . 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 . 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 .