The Tsardom of Bulgaria (Bulgarian: Царство България, romanized: Tsarstvo Balgariya), also known as the Third Bulgarian Tsardom (Bulgarian: Трето Българско Царство, romanized: Treto Balgarsko Tsarstvo), sometimes translated 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.

Prince Ferdinand, founder of the royal family, was crowned as tsar at the Declaration of Independence, mainly because of his military plans and for seeking options for unification of all lands in the Balkans region with an ethnic Bulgarian majority (lands that had been seized from Bulgaria and given to the Ottoman Empire in the Treaty of Berlin). He and his successors were reckoned as kings internationally.

The state was almost constantly at war throughout its existence, lending to its nickname as "the Balkan Prussia". For several years Bulgaria mobilized an army of more than 1 million people from its population of about 5 million, and in the 1910s it engaged in three wars – the First and Second Balkan Wars, and the First World War. Following the First World War the Bulgarian army was disbanded and forbidden to exist by the Allied Powers, and all plans for national unification of the Bulgarian lands failed.

Less than two decades later Bulgaria entered the Second World War on the side of the Axis Powers and once again found itself on the losing side, until it switched sides to the Allies in September 1944. In 1946, the monarchy was abolished, its final tsar was sent into exile, and the tsardom was replaced by the People's Republic of Bulgaria.

Despite the establishment of the Principality of Bulgaria (subject to Ottoman suzerainty) in 1878, and the subsequent Bulgarian control over Eastern Rumelia after 1885, there was still a substantial Bulgarian population in the Balkans living under Ottoman rule, particularly in Macedonia. To complicate matters, Serbia and Greece too made claims over parts of Macedonia, while Serbia, as a Slavic nation, also considered Macedonian Slavs as belonging to the Serbian nation. Thus began a three-sided struggle for control of these areas which lasted until World War I. In 1903 there was a Bulgarian insurrection in Ottoman Macedonia.

In 1908 Ferdinand used the struggles among the Great Powers to declare Bulgaria an independent kingdom with himself as Tsar. He did this on 5 October (though celebrated on 22 September, as Bulgaria remained officially on the Julian Calendar until 1916) in the St Forty Martyrs Church in Veliko Tarnovo. Even before then, however, Bulgaria had only acknowledged the overlordship of the sultan formally. Since 1878, Bulgaria had had its own constitution, flag, and anthem, and conducted a separate foreign policy.

Ferdinand took the Bulgarian title "Tsar" in honor of the rulers of the First and Second Bulgarian Empires. However, while previous Bulgarian "tsars" were reckoned as emperors, Ferdinand and his successors were called "kings" outside Bulgaria. The Tarnovo Constitution was retained, with the word "tsar" replacing the word "prince" or ''knyaz''.

In 1911 the Nationalist Prime Minister Ivan Geshov set about allying with Greece and Serbia, and the three allies agreed to put aside their rivalries to plan a joint attack on the Ottomans.

In February 1912 a secret treaty was signed between Bulgaria and Serbia, which was firstly against Austria-Hungary, but also then redirected by Bulgaria to be against the Ottoman Empire and in May 1912 a similar treaty was signed with Greece. Montenegro was also brought into the pact. The treaties provided for the partition of Macedonia and Thrace between the allies, although the lines of partition were left dangerously vague. After the Ottomans refused to implement reforms in the disputed areas, the First Balkan War broke out in October 1912.

The allies had astonishing success. The Bulgarian army inflicted several crushing defeats on the Ottoman forces and advanced threateningly against Constantinople, while the Serbs and the Greeks took control of Macedonia. The Ottomans sued for peace in December. Negotiations broke down, and fighting resumed in February 1913. The Ottomans lost Adrianople to a Bulgarian task force. A second armistice followed in March, with the Ottomans losing all their European possessions west of the Midia-Enos line, not far from Istanbul. Bulgaria gained possession of most of Thrace, including Adrianople and the Aegean port of Dedeagach (today Alexandroupoli). Bulgaria also gained a slice of Macedonia, north and east of Thessaloniki, but only some small areas along her western borders.

Bulgaria sustained the heaviest casualties of any of the allies, and on this basis felt entitled to the largest share of the spoils. The Serbs, in particular, did not see things this way and refused to vacate any of the territories they had seized in northern Macedonia (that is, the territory roughly corresponding to the modern Republic of North Macedonia), stating that the Bulgarian army had failed to accomplish its pre-war goals at Adrianople (i.e., failing to capture it without Serbian help) and that the pre-war agreements on the division of Macedonia had to be revised. Some circles in Bulgaria inclined toward going to war with Serbia and Greece on this issue. In June 1913 Serbia and Greece formed a new alliance, against Bulgaria. The Serbian Prime Minister, Nikola Pasic, told Greece it could have Thrace if Greece helped Serbia keep Bulgaria out of the Serbian part of Macedonia, and the Greek Prime Minister Eleftherios Venizelos agreed. Seeing this as a violation of the pre-war agreements, and discreetly encouraged by Germany and Austria-Hungary, Tsar Ferdinand declared war on Serbia and Greece and the Bulgarian army attacked on June 29. The Serbian and the Greek forces were initially on the retreat on the western border, but they soon took the upper hand and forced Bulgaria into retreat. The fighting was very harsh, with many casualties, especially during the key Battle of Bregalnica. Soon Romania entered the war and attacked Bulgaria from the north. The Ottoman Empire also attacked from the southeast. The war was now lost for Bulgaria, which had to abandon most of her claims of Macedonia to Serbia and Greece, while the revived Ottomans retook Adrianople. Romania took possession of southern Dobruja.

In the aftermath of the Balkan Wars, Bulgarian opinion turned against Russia and the Western powers, whom Bulgarians felt had done nothing to assist them. Bulgaria, Romania, and Greece initially remained neutral, observing the course of the war before deciding where their sympathies lay.

Under the government of Vasil Radoslavov, Bulgaria aligned itself with Germany and Austria-Hungary, despite this entailing becoming an ally of the Ottomans, Bulgaria's traditional adversary. However, Bulgaria had relinquished its claims against the Ottomans, while Serbia, Greece, and Romania (allies of the UK and France) held territories perceived as Bulgarian by Bulgaria. Recuperating from the Balkan Wars, Bulgaria remained neutral during the first year of World War I. When Germany pledged to restore the boundaries of the Treaty of San Stefano, Bulgaria, boasting the largest army in the Balkans, declared war on Serbia in October 1915. Subsequently, the UK, France, Italy, and Russia declared war on Bulgaria.

Bulgaria, allied with Germany, Austria-Hungary, and the Ottomans, achieved military victories against Serbia and Romania. They captured much of Macedonia (including Skopje in October), advanced into Greek Macedonia, and seized Dobruja from the Romanians in September 1916. However, the war quickly became unpopular among the majority of Bulgarians, who endured severe economic hardship and resented fighting alongside their fellow Orthodox Christians while allied with the Muslim Ottomans. Aleksandar Stamboliyski, leader of the Agrarian Party, was imprisoned for his opposition to the war. The Russian Revolution of February 1917 significantly impacted Bulgaria, spreading antiwar and anti-monarchist sentiments among troops and in cities. In June, Radoslavov's government resigned, mutinies erupted in the army, Stamboliyski was released, and a republic was proclaimed.

In September 1918, the French, Serbs, British, Italians, and Greeks broke through on the Macedonian front, compelling Tsar Ferdinand to seek peace. Stamboliyski advocated for democratic reforms rather than a revolution. To preempt the revolutionaries, he persuaded Ferdinand to abdicate in favor of his son, Boris III. The revolutionaries were suppressed, and the army was disbanded. Under the Treaty of Neuilly-sur-Seine (November 1919), Bulgaria lost its Aegean coastline (Western Thrace) to Greece, parts of its Macedonian territory and the Western Outlands to the new Kingdom of Yugoslavia, and Southern Dobruja was returned to the Kingdom of Romania. The country was required to reduce its army to no more than 20,000 men and pay reparations exceeding $100 million. Bulgarians generally refer to the treaty's outcomes as the "Second National Catastrophe." In elections held in March 1920, the Agrarians secured a substantial majority, and Stamboliyski formed Bulgaria's first genuinely democratic government.

After World War I, Bulgaria had already lost a significant amount of territory, including its coast to the Aegean Sea with Dede Agach (Alexandroupoli), which was crucial for the Bulgarian economy, as well as the Western Outlands. The 1879 constitution did not clearly delineate the powers of the king and Parliament, a common issue in constitutional monarchies. While the framers of the 1879 constitution intended to vest most of the power in Parliament, a sufficiently cunning monarch could still potentially seize control of the government machinery. This proved to be the case with Tsar Ferdinand, who, however, was compelled to abdicate after successive defeats in the Balkan Wars and World War I. His son, Boris, then ascended to the throne, but the young king could not replicate the political influence his father had amassed over three decades of intrigue. Furthermore, Boris did not command the same level of moral authority that his father had established.

Parliament came to dominate after Boris appointed Aleksandar Stamboliyski as prime minister. Stamboliyski's Agrarian Party soon gained control of Parliament, holding over half of the seats. The remaining seats were held by the Bulgarian Communist Party, the country's second-largest political party and the only other significant one (several minor parties had no representation in Parliament or real significance). The Agrarian Party primarily represented disgruntled peasants, particularly those dissatisfied with the government in Sofia during Ferdinand's corrupt reign, which exploited and stole from the peasantry. While most lower-class Bulgarians supported Macedonia's annexation, they were dismayed by the heavy casualties suffered in two unsuccessful wars to reclaim it. Stamboliyski himself spent the war years in jail for vehemently criticizing these wars. On the other hand, the Bulgarian Communist Party drew support mainly from the intelligentsia and urban professionals, with its primary base consisting of the poorest peasants and minorities. In contrast, the Agrarian Party represented wealthier peasants. In this climate, Stamboliyski swiftly enacted a 1920 land reform aimed at breaking up state properties, church lands, and holdings of wealthy peasants. Predictably, this garnered widespread support and pushed the Bulgarian Communist Party into an alliance with the Agrarian Party to gain parliamentary representation.

Stamboliyski faced significant social problems in what was still a poor country, inhabited mostly by peasant smallholders. Bulgaria was burdened with substantial war reparations to Yugoslavia and Romania and had to contend with the issue of refugees, as pro-Bulgarian Macedonians were forced to leave Yugoslav Macedonia. Nevertheless, Stamboliyski was able to push through many social reforms, despite strong opposition from the Tsar, landlords, and the officers of the significantly reduced but still influential army. Another formidable adversary was the Internal Macedonian Revolutionary Organization (VMRO), which advocated for war to regain independence for Macedonia. Faced with this array of enemies, Stamboliyski allied himself with the Bulgarian Communist Party and established relations with the Soviet Union.

Stamboliyski immediately embarked on drastic economic reforms. He abolished the mercantile monopoly on grain and replaced it with a state syndicate, dismantled large urban and rural estates and sold the surplus to the poor, introduced compulsory labor laws to alleviate post-war unemployment, implemented a progressive income tax, and made secondary education mandatory. All aspects of this radical reform policy were designed to eliminate "noxious" classes such as lawyers, usurers, and merchants, distribute wealth and responsibilities more equitably across society, and improve the living standards of landless and poor peasants. In foreign policy, Stamboliyski officially renounced Bulgaria's territorial claims, which he associated with a standing army, monarchy, and large government expenditures—phenomena that peasants considered outdated. With no major power available to protect Bulgarian interests in the Balkans post-war, the traditional foreign policy approach was abandoned in favor of reconciliation with all European powers, the new government of Kemal Ataturk in Turkey, membership in the League of Nations, and friendship with the new Kingdom of Serbs, Croats, and Slovenes (later the Kingdom of Yugoslavia). Bulgaria's support for Atatürk's Turkish Republic in 1920 significantly improved relations with Turkey. Reconciling with Yugoslavia was crucial for Stamboliyski's vision of establishing a multiethnic Balkan Peasants' Federation. Better relations with Yugoslavia depended on suppressing the powerful Macedonian extremist movement. Therefore, in 1921, Stamboliyski initiated a two-year period of severe repression against the IMRO; by 1923, Bulgaria and Yugoslavia agreed at the Nis Convention to collaborate in combating extremism.

Stamboliyski was a staunch anti-communist and aimed to create an international movement to counter Marxism. This effort was known as his "Green International," in opposition to the communist "Red International." He traveled to Eastern European capitals promoting his vision of a peasant alliance. However, trouble arose when he attempted to spread this movement into Yugoslavia, a country with conditions very similar to Bulgaria—little industry and a significant communist presence. Stamboliyski was well-liked in Belgrade due to his support for a peaceful resolution to the Macedonia issue. He also advocated for uniting all Slavic-speaking nations in Eastern Europe into a large Yugoslav confederation. However, he encountered difficulties due to the militant faction of IMRO back home. Many Macedonian leaders had relocated to Sofia after the failed 1903 revolt against the Ottoman Empire, and they were now joined by others fleeing the Yugoslav government, which officially claimed Macedonians as ethnic Serbs. Bulgaria, having been compelled to reduce its armed forces after World War I, saw IMRO leaders gain control over much of the border area with Yugoslavia.

Under the leadership of a large Macedonian group in Sofia, the remaining strong nationalist elements in Bulgaria found the new pacifist policy alarming. The urban working class, which did not benefit from the agrarian reforms, gravitated towards the Communists or the Socialist Workers. Inflation and industrial exploitation continued unabated. Many of Stamboliyski's subordinates exacerbated social tensions by adopting rigid positions in favor of peasant rights. The National Alliance, a confederation that had been dormant since the war, reorganized the Bulgarian right. In 1922, its leaders were imprisoned by Stamboliyski's Orange Guard, temporarily stifling its activities. Meanwhile, in late 1922 and early 1923, Macedonian nationalists seized Kyustendil on the Yugoslav border. They assaulted government officials in protest against the reconciliation with Yugoslavia and the Kingdom of Greece. Stamboliyski responded with mass arrests, an intensified campaign against IMRO terrorism, a purge of his own fractured and notoriously corrupt party, and called for new parliamentary elections. These measures united diverse opponents of the Agrarians—including IMRO, the National Alliance, army factions, and social democrats—into a coalition led by Aleksandar Tsankov. The Communists remained outside this coalition. Bulgaria's Western creditors, disenchanted with a government that had rejected their reparations policy, refrained from intervening. In June 1923, IMRO agents brutally assassinated Stamboliyski, paving the way for the conspirators to seize control of the entire country. Despite scattered and ineffective peasant resistance, they consolidated their grip on power.

In March 1923 Stamboliyski signed an agreement with Yugoslavia recognizing the new border and agreeing to suppress IMRO. This triggered a nationalist reaction, and on 9 June there was a coup organized by the armed forces under General Ivan Valkov's Military Union with support from the Tsar and other right-wing elements of the Tsardom after the AP controlled 87% of Parliament in the elections that year. The Bulgarian government could only muster a handful of troops to resist and even worse was a peasant mob with no guns rallied by Stamboliyski. Despite this, the streets of Sofia erupted in chaos and the hapless prime minister was lynched in addition to attacks on unarmed peasants.

The whole affair seriously tar brushed Bulgaria's international image. A right-wing government under Aleksandar Tsankov took power, backed by the Tsar, the army, and the VMRO.

The September Uprising began in 1923, after the 9 June coup d'état, when Alexander Stamboliyski was planning to capture Pazardzhik with his sympathizers to restore his power, which was quickly disrupted by the Bulgarian Army. He was then captured and relocated to Slavovitsa, his birthplace, where he was tortured and killed by IMRO agents. Tsankov's government arrested over 2000 alleged communists in which uprisings began. Vasil Kolarov and Georgi Dimitrov, who were the main leaders of the uprisings, chose Montana as the centre. Many uprisings began in the Northwestern parts of Bulgaria, which were quickly overpowered by the army.

The Communist leader Georgi Dimitrov fled to the Soviet Union. There was savage repression in 1925 following the second of two failed attempts on the Tsar's life in the bomb attack on Sofia Cathedral (the first attempt took place in the mountain pass of Arabakonak). But in 1926, Boris persuaded Tsankov to resign in favour of a more moderate government under Andrey Lyapchev. An amnesty was proclaimed, although the Communists remained banned.

Lyapchev was considered to be more lenient towards the political opposition than Tsankov. The Communists re-emerged in 1927 under the guide of the political party Bulgarian Workers' Party. An independent workers' trade union became the centre of workers' political activity. Under the Macedonian prime minister, the IMRO also had much more freedom. This meant that political assassinations and acts of terrorism could continue unabated. IMRO raids into Yugoslavia ended Bulgaria's rapprochement with that country. The Macedonians demanded preferential economic treatment under Liapchev. the late 1920s brought relative political stability to Bulgaria compared with the previous years. Lyapchev was the leader of a conservative majority in the Sabranie. The press was relatively free, and the institutions of education and the judiciary were functioning independently. Output in industry and agriculture was finally above pre-war levels, and foreign investment was on the rise. But even after being substantially reduced, Bulgaria's reparations payments in 1928 amounted to 20 per cent of its budget, and the return to the Gold standard in that year weakened the economy a year before the Great Depression began. In foreign policy, Lyapchev tried unsuccessfully to improve the terms of British and French reparations from the First World War and to bring Bulgaria out of its post-war diplomatic isolation. The country had already improved its international image through its enthusiastic participation in the League of Nations. In 1926, Bulgaria returned the favour by forcing Greek invading troops to leave southern Bulgaria during the Incident at Petrich. The Macedonian independence movement split over the ultimate goal of its activities in the late 1920s. The supremacist faction sought the incorporation of all Macedonian territory into Bulgaria. The federalist faction (including the IMRO) sought an autonomous Macedonia that could join Bulgaria or Yugoslavia in a protective alliance in the event of a war.

The first daily radio broadcasts appeared in 1930. There were many radio broadcasters such as Radio Sofia (now Radio Bulgaria).

The Agrarians reorganized and won elections in 1931 under the leadership of Nikola Mushanov.

Just when political stability had been restored, the full effects of the Great Depression hit Bulgaria, and social tensions rose again. In May 1934 there was another coup by the military organization Zveno, an authoritarian regime headed by Colonel Kimon Georgiev was established. They dissolved all parties and trade unions and suppressed the IMRO. Their government introduced a corporatist economy, similar to that of Benito Mussolini's Italy. After participating in the Bulgarian coup d'état of 1934, Zveno supporters declared their intention to immediately form an alliance with France and to seek the unification of Bulgaria into an Integral Yugoslavia.

In April 1935 Boris III staged a counter-coup with the help of monarchist Zveno member General Pencho Zlatev and took power himself. The political process was controlled by the Tsar, but a form of parliamentary rule was re-introduced. However, political parties remained banned, and uncharismatic prime ministers were appointed by the monarch. He didn't restore the traditional political supremacy of the Sabranie and write a new constitution. In 1936 a broad coalition, the People's Constitutional Bloc, brought together nearly all leftist and centrist factions in a nominal opposition that had the blessing of the tsar. Boris delayed holding a national election until 1938. At that time, only individual candidates were allowed in a carefully controlled election procedure that excluded party candidate lists. Boris claimed that domination of the new subranie by pro-government representatives justified his non-party system, although the People's Constitutional Bloc seated over sixty delegates. Elections in the next two years were strictly limited in order to maintain Boris's control over his parliament.

With the rise of the "King's government" in 1935, Bulgaria entered an era of prosperity and astounding growth, which deservedly qualifies it as the Golden Age of the Third Bulgarian Kingdom. It lasted nearly five years, governed by prime minister Georgi Kyoseivanov. Kyoseivanov's Premiership oversaw the trials of the instigators of the 1934 military coup and also concluded pacts with Yugoslavia and Greece as Nazi Germany undertook a policy of economic isolation of the Balkans. His government also oversaw a policy of rearmament after a treaty concluded with Ioannis Metaxas overturned the military clauses of the Treaty of Neuilly-sur-Seine and the Treaty of Lausanne. Although the signing of the Salonika Agreement of 1938 restored good relations with Yugoslavia and Greece, the territorial issue continued to simmer.

The government of the Kingdom of Bulgaria under Prime Minister Georgi Kyoseivanov declared a position of neutrality upon the outbreak of World War II. Bulgaria was determined to observe it until the end of the war, but it hoped for bloodless territorial gains to recover the territories lost in the Second Balkan War and World War I, as well as gain other lands with a significant Bulgarian population occupied by neighboring countries. However, it was clear that the central geopolitical position of Bulgaria in the Balkans would inevitably lead to strong external pressure from both World War II factions. On 15 February 1940, following the resignation of Georgi Kyoseivanov, a pro-German Bogdan Filov was appointed Prime Minister of the Kingdom of Bulgaria. On 7 September 1940 Bulgaria succeeded in negotiating the recovery of Southern Dobruja in the Axis-sponsored Treaty of Craiova. Bulgaria also had a non-aggression pact with Turkey.

On 1 March 1941 Bulgaria formally signed the Tripartite Pact, becoming an ally of Nazi Germany, the Empire of Japan, and the Kingdom of Italy. German troops entered the country in preparation for the German invasions of the Kingdom of Greece and the Kingdom of Yugoslavia. When Yugoslavia and Greece were defeated, Bulgaria was allowed to occupy all of Greek Thrace and most of Macedonia. Bulgaria declared war on Britain and the United States but resisted German pressure to declare war on the Soviet Union, fearful of pro-Russian sentiment in the country.

In August 1943 Tsar Boris died suddenly after returning from Germany from heart failure, but also rumoured to be poisoned. He was later succeeded by his six-year-old son Simeon II. Power was held by a council of regents headed by the young Tsar's uncle, Prince Kiril, Bogdan Filov and Nikola Mihov. The new prime minister, Dobri Bozhilov, was in most respects a German puppet. Resistance to the Germans and the Bulgarian regime was widespread by 1943, coordinated mainly by the communists. Together with the Agrarians, now led by Nikola Petkov, the Social Democrats, and even many army officers they founded the Fatherland Front. Partisans operated in the mountainous west and south. By 1944 it was obvious that Germany was losing the war and the regime began to look for a way out. On 1 June 1944 Filov sacked Bozhilov, in the hope of placating internal opposition and the Allies. Filov had reluctantly decided the alliance with Germany should end. His successor Ivan Bagryanov tried to arrange negotiations with the western Allies.

Meanwhile, the capital Sofia was bombed by Allied aircraft in 1941 until 1944. But it was the Red Army which was rapidly advancing towards Bulgaria. In August 1944 Bulgaria unilaterally announced its withdrawal from the war and asked the German troops to leave: Bulgarian troops were hastily withdrawn from Greece and Yugoslavia. In September, the Soviets crossed the northern border. The government, desperate to avoid a Soviet occupation, declared war on Germany, but the Soviets could not be put off, and on September 8, they declared war on Bulgaria – which thus found itself for a few days at war with both Germany and the Soviet Union. The Soviet Union occupied the north-eastern part of Bulgaria along with the key port cities of Varna and Burgas by the next day. By order of the government, the Bulgarian Army offered no resistance. On September 16, the Red Army entered Sofia. During the same day, a pro-Axis government-in-exile was established in Vienna under Aleksandar Tsankov and while it was able to muster a 600-strong Bulgarian SS regiment of Bulgarian anti-communist volunteers already in Germany under a German commander, they had little success.

The Holocaust in Bulgaria was the persecution of Jews between 1941 and 1944 in the Kingdom of Bulgaria and their deportation and annihilation in the Bulgarian-occupied regions of Yugoslavia and Greece during World War II, arranged by the Nazi Germany-allied government of Tsar Boris III and prime minister Bogdan Filov. The persecution began in 1941 with the passing of anti-Jewish legislation and culminated in March 1943 with the arrest and deportation of almost all – 11,343 – of the Jews living in Bulgarian-occupied regions of Northern Greece, Yugoslav Macedonia and Pirot. These were deported by the Bulgarian authorities and sent to extermination camps in German-occupied Poland.

The deportation of the 48,000 Jews from Bulgaria proper was subsequently initiated but halted following widespread protests. Upon becoming aware of the impending plans members of parliament led by Dimitar Peshev pressured the interior minister to revoke the initial deportation order, while public protests and interventions by prominent figures, notably Bulgarian Orthodox Church bishops Stefan of Sofia and Kiril of Plovdiv, persuaded the Tsar first to stop the deportation temporarily in March 1943, and two months later to postpone it indefinitely. The Jews whose deportation from Bulgaria was halted, including all Sofia's 25,743 Jews, were instead internally deported to the countryside and had their property confiscated, and Jewish males between the ages of 20 and 46 were conscripted into the Labour Corps until September 1944. The events that prevented the deportation to extermination camps of about 48,000 Jews in spring 1943 are termed the "Rescue of the Bulgarian Jews". The survival rate of the Jewish population in Bulgaria as a result was one of the highest in Axis Europe.

The Fatherland Front took office in Sofia following a coup d'état, setting up a broad coalition under the former ruler Kimon Georgiev. Under the terms of the peace settlement Bulgaria was allowed to keep Southern Dobruja, but formally renounced all claims to Greek and Yugoslav territory. 150,000 Bulgarians were expelled from Greek Thrace. The Communists deliberately took a minor role in the new government at first, but the Soviet representatives were the real power in the country. A Communist-controlled People's Militia was set up, which harassed and intimidated non-Communist parties.

The new realities of power in Bulgaria were shown when the former regents and hundreds of other officials of the old regime who were arrested on charges of war crimes were executed on 1 February 1945. In September 1946, the monarchy was abolished by plebiscite. This referendum violated the Tarnovo Constitution, which stated that any change in the form of the state could only take place if a Grand National Assembly was convened by the Tsar (in practice, the Tsar acting on the advice of the government). The republic was formally proclaimed a week later, and the young Tsar Simeon was forced into exile. The Communists now openly took power, with Vasil Kolarov becoming president and Dimitrov becoming prime minister. Free elections promised for 1946 were blatantly rigged and were boycotted by the opposition. The Agrarians refused to co-operate with the new regime, and in June 1947 their leader Nikola Petkov was arrested. Despite strong international protests, he was executed in September. This marked the Dimitrov Constitution to be introduced and also an establishment of a Communist regime in Bulgaria.