World War II: The Fatherland Front takes power in Bulgaria through a military coup in the capital and armed rebellion in the country. A new pro-Soviet government is established.

The Fatherland Front was a Bulgarian pro-communist political resistance movement, which began in 1942 during World War II. The Zveno movement, the communist Bulgarian Workers Party, a wing of the Bulgarian Agrarian National Union and the Bulgarian Social Democratic Workers Party all became part of the OF. The constituent groups of the OF had widely contrasting ideologies and had united only in the face of the pro-German militarist dictatorship in Bulgaria. At the beginning, the members of the OF worked together, without a single dominating group. Professional associations and unions could be members of the front and maintain their organisational independence. However, the Bulgarian Communist Party soon began to dominate. In 1944, after the Soviet Union had declared war on Bulgaria, the OF carried out a coup d'état and declared war on Germany and the other Axis powers. The OF government, headed by Kimon Georgiev of Zveno, signed a ceasefire treaty with the Soviet Union. In the summer of 1945 most of BANU led by Nikola Petkov and most of the Social-Democrats had left the OF and became a large opposition group which later on after the 1946 Grand National Assembly election would become a coalition named "Federation of the village and urban labour" with 99 MPs out of 465.

The Tsardom of Bulgaria, also known as the Third Bulgarian Tsardom, usually known in English as the Kingdom of Bulgaria, or simply Bulgaria, was a constitutional monarchy in Southeastern Europe, which was established on 5 October [O.S. 22 September] 1908, when the Bulgarian state was raised from a principality to a tsardom.

The 1944 Bulgarian coup d'état, also known as the 9 September coup d'état, was a coup that overthrew the government of Kingdom of Bulgaria on the eve of 9 September 1944. During the People's Republic of Bulgaria it was called using the propaganda term People's Uprising of 9 September - on the grounds of the broad unrest and Socialist Revolution - as it was a turning point politically and the beginning of radical reforms towards Soviet-style socialism.