In 1948 the newly formed Soviet empire in Eastern Europe was threatened by a split between Yugoslav President Josip Broz Tito and Soviet leader Joseph V. Stalin. After expelling Yugoslavia from the Cominform, Stalin began exerting greater pressure on the other East European states, including Bulgaria, to adhere rigidly to Soviet foreign and domestic policy. He demanded that the communist parties of those countries become virtual extensions of the Communist Party of the Soviet Union (CPSU) by purging all opposition figures. The Bulgarian government curtailed religious freedom by forcing Orthodox clergy into a Union of Bulgarian Priests in 1948, taking control of Muslim religious institutions, and dissolving Bulgarian branches of Roman Catholic and Protestant churches in 1949. The most visible political victim of the new policy was Traicho Kostov, who with Georgi Dimitrov and Vasil Kolarov had led the BCP to power in 1944. Accused by Dimitrov of treason, Kostov was shot in December 1949. Dimitrov died before Kostov's execution, Kolarov soon afterward. To fill the power vacuum left by those events, Stalin chose Vulko Chervenkov, a trusted protégé. Chervenkov would complete the conversion of the BCP into the type of one-man dictatorship that Stalin had created in the Soviet Union. Chervenkov assumed all top government and party positions and quickly developed a cult of personality like that of his Soviet mentor. At Stalin's command, Chervenkov continued purging party members from 1950 until 1953, to forestall in Bulgaria the sort of Titoist separatism that Stalin greatly feared. Rigid party hierarchy replaced the traditional informal structures of Bulgarian governance, and the purges eliminated the faction of the BCP that advocated putting Bulgarian national concerns ahead of blind subservience to the CPSU.

The Chervenkov period (1950-56) featured harsh repression of all deviation from the party line, arbitrary suppression of culture and the arts along the lines of Soviet-prescribed socialist realism, and an isolationist foreign policy. By early 1951, Chervenkov had expelled one in five party members, including many high officials, in his campaign for complete party discipline. In 1950 a new agricultural collectivization drive began. In spite of intense peasant resistance, the collectivization drive continued intermittently until the process was virtually complete in 1958.

Data as of June 1992