After September 9, the Bulgarian Communist Party emerged from two decades of clandestine existence to become the leading political force in the country. Initially their radicalism was hidden behind the ostensibly moderate Fatherland Front government led by political veteran Kimon Georgiev, principal architect of the 1934 coup. However, the Communist Party's domination of the Front was never in doubt. Manipulating the ministries of Justice and the Interior to cow right-wing collaborators, and driving the left and centre parties into opposition by repeated provocations, the Party increased its membership from 15,000 to 250,000 in six months. Dominant in government, they then staged a referendum on the monarchy , abolished it, and proclaimed the People's Republic on September 15, 1946.

Now controlled by Georgi Dimitrov, Vasil Kolarov and Anton Yugov , the state apparatus was turned against the opposition. Many of the political parties left outside the Communist-controlled Fatherland Front had boycotted Bulgaria's first postwar elections in 1945, convinced that the presence of the Red Army on Bulgarian soil would intimidate voters into backing the Front.

A more organized campaign was mounted for the general elections of October 1946, producing a parliament that included a small but vociferous number of anti-Communist MPs. The opposition centred around the Agrarian party or BZNS , heir to the popular radical tradition of Stamboliiski, and leaders of peasant resistance to enforced collectivization of the countryside. The Communists claimed that they were traitors sabotaging the economic recovery of the nation: hundreds of BZNS party workers were purged and their leader, Nikola Petkov , was hanged for "treason" after a show trial in 1947. Other parties outside the Front were snuffed out at the same time. The same year, Bulgaria acquired the new "Dimitrov" Constitution (modelled on the USSR's) and the nationalization of 2273 enterprises struck the "bourgeoisie" a mortal blow.

The following year saw a power struggle within the Party, largely over economic links with the Soviet Union and relations with Tito's Yugoslavia . The Tito-Stalin row of 1948 and Yugoslavia's subsequent expulsion from the Soviet camp gave Communist leaders everywhere the chance they needed to get rid of comrades who they found troublesome. Moscow-trained cadres targeted "homegrown" Communists - that is those who had chosen to remain in the country during the interwar years rather than flee to the USSR - in an attempt to settle old scores.

Some of the more patriotic Bulgarian Communists criticized the terms of Bulgaro-Soviet trade (eighty percent of Bulgaria's tobacco crop was purchased at below market prices and then undersold abroad), leaving themselves open to accusations of nationalism at a time when blind loyalty to the Soviet Union was the order of the day - as good a reason as any to launch a purge of "Titoists". Ten ministers, six Politburo members (including Traicho Kostov , shot after renouncing his "confession" to having been a fascist spy since 1942) and 92,500 lesser Party members were arrested or dismissed in the purge of 1948-49, while the nation was paralysed by police terror . Stalinism per vaded Bulgaria, and for his total sycophancy the Party leader who succeeded Dimitrov, Vâlko Chervenkov , was dubbed "little Stalin".