Bulgaria in the Second World War

Bulgaria's history during the Second World War falls into three main periods: initial neutrality until 1 March 1941, alliance with the Axis until 9 September 1944, and participation on the Allied side until the end of the conflict. Until the 1990s, Bulgarian historiography largely neglected the country's involvement on the Axis side, while calling its participation with the Allies the 'Patriotic War', following the Soviet model. During the war, the Bulgarian army carried out several partial mobilisations in response to the military and political situation.

In July–August 1939, several formations were deployed to cover the south-eastern frontier in the event of conflict with Turkey. When Bulgaria joined the Tripartite Pact in early 1941, its units were at peacetime strength; some were then mobilised. Mobilisation in February and March 1941 almost tripled the army's size. It increased again after Britain and the United States declared war in late 1941. In 1944, the army expanded to 447,000 men, filling the ranks of 11 divisions and four brigades.

After the war, the First Bulgarian Army was welcomed back from the front in Sofia on 17 June 1945. The Versailles peace settlement of 1919 had ended the First World War by placing blame solely on the defeated, laying the groundwork for the Second World War. Nationally humiliated and deprived of their own armies, the defeated states became centres of revanchism. Germany led calls to revise the peace treaties, particularly after Hitler came to power in 1933. Italy also pursued expansion. In these circumstances, Bulgaria's best course was to preserve its neutrality and freedom from alliances while seeking peaceful treaty revision.

Bulgaria's war against Germany can be divided into two phases. The first lasted from September to the end of November 1944. Bulgarian troops operated in Macedonia, eastern Serbia and Kosovo. Bulgaria deployed its First, Second and Fourth Armies, while the Third Army remained on the Turkish frontier. To participate effectively, the army mobilised and deployed its forces strategically. By 1 October 1944, total strength had reached about 445,000.

After the events of 9 September 1944, Bulgarian troops, together with partisan and Soviet units, repelled German attacks along the Kyustendil–Sofia axis. On 11 September, a German reconnaissance company passed through Kula and reached Voynitsa unopposed, but withdrew after exchanging fire with Bulgarian soldiers and partisans. On 18 September 1944, the Bulgarian army came under Marshal Fyodor Tolbukhin of the Third Ukrainian Front. Mobilisation began on 18 September and ended that month. The army was tasked with covering the Red Army's left flank, defeating the enemy in Serbia and Vardar Macedonia, and blocking German troops retreating from Greece.

The second phase lasted from December 1944 to May 1945. The Bulgarian army helped liberate northern Yugoslavia and entered southern Hungary and eastern Austria. Bulgaria deployed 110,000 soldiers in the First Bulgarian Army. The Srem operation took place in December 1944, after which fighting moved to Hungary and Austria. The Drava operation followed in March 1945, and by the end of that month Bulgarian forces concentrated near the River Mur. The final engagements against German troops took place in Austria, Slovenia and Bosnia until May 1945. The Bulgarian army continued fighting until Nazi Germany's surrender on 9 May 1945.

Despite demonstrating strong fighting ability in Hungary and Yugoslavia and contributing to Nazi Germany's final defeat, Bulgaria remained internationally isolated and fell within the Soviet sphere of influence. At the Potsdam Conference, Joseph Stalin proposed recognising Bulgaria as a co-belligerent, as had been done for Italy. Harry Truman and Winston Churchill refused to discuss this before elections and the restoration of liberal democracy, in accordance with the Yalta Conference. Bulgaria was required to feed 200,000 Soviet troops stationed in the country until the Paris Peace Treaty was signed in 1947.

A referendum took place on 8 September 1946 in the presence of Soviet troops, after which Bulgaria was proclaimed a 'people's republic'. The new prime minister, Georgi Dimitrov, began a gradual transition to communist government and a totalitarian state. He promoted close relations with communist Yugoslavia and the Macedonisation of the population in Macedonia, aiming at union between Bulgaria and Yugoslavia. The peace treaty signed in 1947 following the Paris Peace Conference restored Bulgaria's borders to those before its accession to the Tripartite Pact in 1941. Bulgaria was required to demilitarise its southern frontier and pay reparations. It was not granted co-belligerent status, unlike Italy.

After another referendum, again held in the presence of Soviet troops, a republican constitution known as the Dimitrov Constitution was adopted in 1947. It established the legal foundations of the communist regime that ruled for the following decades. Bulgaria developed close ties with the USSR and became its satellite.