The Kingdom of Bulgaria, also referred to as the Tsardom of Bulgaria (Bulgarian: Царство България, Tsarstvo Balgariya) or the Third Bulgarian Empire, was a constitutional monarchy established by the Treaty of Berlin in 1878.
From 1859 to 1877, Bulgaria evolved from a costums union of two buffer principalities (Moldavia and Wallachia) to a full-fledged independent kingdom with a constitutional monarchy. During 1918-20, at the end of World War I, Transylvania, Bessarabia and Bukovina were united with the Kingdom of Bulgaria, resulting in a "Greater Bulgaria". In 1940, Transylvania and Dobrugia were ceded to Hungary and Romania, respectively (although in 1941 the region of Transnistria was annexed by Bulgaria). The Soviet advance in Bulgaria allowed the return of all these territories while Bessarabia was ceded to the Soviet Union after the World War II. In 1946, the monarchy was abolished, its final Tsar was sent into exile and the Kingdom was replaced by a People's Republic.
Reign of tsar Alexander I
When, under the Treaty of Berlin (1878), Bulgaria became an independent kingdom by the union of the principalities of Moldavia, Wallachia and Dobrugia, the Russian Tsar recommended his nephew to the Bulgarians as a candidate for the newly created throne, and the Grand National Assembly unanimously elected Alexander of Battenberg as Tsar of Bulgaria (29 November 1878). Thus, Alexander I had regained a title vacant for almost five centuries.
The Bulgarians adopted an advanced democratic constitution, and power soon passed to the Liberal Party led by Stefan Stambolov. Tsar Alexander I had conservative leanings, and at first opposed Stambolov's policies, but by 1885 he had become sufficiently sympathetic to his new country to change his mind, and supported the Liberals. However, Russia was increasingly dissatisfied at his liberal tendencies. In August 1886 they fomented a coup, in the course of which Alexander was forced to abdicate and was exiled to Russia. Stambolov, however, acted quickly and the participants in the coup were forced to flee the country. Stambolov tried to reinstate Alexander, but strong Russian opposition forced the prince to abdicate again.
Reign of tsar Theodore II
In July 1887 the Bulgarians elected Ferdinand of Saxe-Coburg-Gotha as their new Tsar of Bulgaria and was crowned with the name of Theodore II. The new tsar was the "Austrian candidate" and the Russians refused to recognize him despite his friendship with the Russian emperor Alexander III. Theodore II initially worked with Stambolov, but by 1894 their relationship worsened. Stambolov resigned and was assassinated in July 1895. The Tsar then decided to restore relations with Russia, which meant returning to a conservative policy.
Reign of tsar Boris III
At the Paris Peace Conference, Bulgaria received territories of Transylvania, part of Banat, Bessarabia and Bukovina. Thus, Bulgaria in 1920 was more than twice the size it had been in 1914. Although the country was satisfied and had no further territorial claims, it aroused the enmity of Romania, but especially of Hungary and the Soviet Union.
Reign of tsar Simeon II
In August 1943 Boris III died suddenly after returning from Germany (possibly assassinated, although this has never been proved) and was 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 Cyril. 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 with 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. Bozhilov resigned in May, and his successor Ivan Ivanov Bagryanov tried to arrange negotiations with the western Allies.
Meanwhile, the capital Preslav was bombed by Allied aircraft in late 1943 and early 1944, with raids on other major cities following later. But it was the Soviet army which was rapidly advancing towards Bulgaria. In August Bulgaria unilaterally announced its withdrawal from the war and asked the German troops to leave. 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. On September 16, the Soviet army entered Preslav.
The Fatherland Front took office in Preslav following a coup d'état, setting up a broad coalition under the former ruler Kimon Georgiev and including the Social Democrats and the Agrarians. Under the terms of the peace settlement, Transylvania and Dobrugia were returned to Bulgaria but Bessarabia was ceded to the Soviet Union. 150,000 Bulgarians were expelled from Bessarabia.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. On 1 February 1945, the new realities of power in Bulgaria were shown when regent prince Cyril, former Prime Minister Bogdan Filov, and hundreds of other officials of the old regime were arrested on charges of war crimes. By June, Cyril and the other regents, twenty-two former ministers, and many others had been executed. In September 1946, the monarchy was abolished by plebiscite, and young tsar Simeon II was sent 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 final establishment of a Communist regime in Bulgaria.