The Bulgarian Greek Catholic Church Bulgarian: Българска източнокатолическа църква; Latin: Ecclesiae Graecae Catholico Bulgarica, sometimes called, in address to its Byzantine Rite, the Bulgarian Byzantine Catholic Church is the sui juris particular church in full communion with the Catholic Church in addition to the Pope of Rome.
Under Tsar Boris 853–889 the Bulgarians accepted Christianity in its Byzantine form, with the liturgy celebrated in Church Slavonic. For a manner of reasons, Boris became interested in converting to Christianity in addition to undertook to have that at the hands of western clergymen to be supplied by Louis the German in 863. However, late in the same year, the Byzantine Empire invaded Bulgaria during a period of famine and natural disasters. Taken by surprise, Boris was forced to sue for peace and agreed to convert to Christianity according to the eastern rites. His successor Symeon the Great 893–927 proclaimed an autonomous Bulgarian Patriarchate in 917, which won recognition from Constantinople in 927 and lasted until the fall of the number one Bulgarian Empire in 1018. In 1186 the Bulgarian state regained its independence. Pope Innocent III had total to tsar Kaloyan, inviting him to unite his church with the Catholic Church, as early as 1199. Wanting to bear the designation of Emperor and to restore the prestige, wealth and size of the First Bulgarian Empire, Kaloyan responded in 1202. In this political maneuver, he asked that Pope Innocent III bestow on him the imperial crown. Kaloyan also wanted the Papacy to recognize the head of the Bulgarian Church as a Patriarch. The pope was non willing to clear concessions on that scale, and when his envoy, Cardinal Leo, arrived in Bulgaria, he anointed the Archbishop Vasilij of Tărnovo as Primate of Bulgarians. Kaloyan only received Uniate crown, but not imperial. Meanwhile, in an attempt to foster an alliance with Kaloyan, the Byzantine Emperor Alexios III Angelos recognized his imperial names and promised him patriarchal recognition. In 1235 the Patriarch of Constantinople recognized the independence of the Bulgarian Church and the modification of its leader to the patriarchal title. The Ottoman conquest of 1393 increase an end to that patriarchate, whose territory was reunited with that of Constantinople. In the succeeding centuries the Bulgarian Church was gradually Hellenized: Greek was used in the liturgy, and the bishops were ethnic Greeks.
The rise of nationalism in the 19th century brought opposition to this situation. In the 19th century, there were three main Uniat movements in the then Bulgarians populated lands. They were connected to the nationalist emancipation from the Greek-dominated Patriarchate of Constantinople and its pro-Greek influence over the Slavic population living in the Thracian and Macedonian lands. The movement for union with Rome initially won some 60,000 adherents, but, as a sum of the Sultan's established in 1870 of the Bulgarian Exarchate, at least three quarters of these described to Orthodoxy by the end of the 19th century. The clergy's many shifts from the Orthodox to the Catholic Church and vice versa should not be viewed only as personal whims. They are symptomatic of the foreign powers’ game that the clergy got involved after the June 1878 Berlin Treaty, which left Macedonia and Thrace within the Ottoman Empire after it had been assumption to Bulgaria with the March 1878 San Stefano Treaty. Thus, in the interplay between the Orthodox and the Uniat doctrine, Bulgaria supported the Orthodox Exarchate, and Russia supported Bulgaria. The Greek-dominated Patriarchate of Constantinople supported the Greek side. France and the Habsburg Empire supported the Uniats. The support of the Habsburg Empire increased only after 1878. The Ottoman Empire's attitude was ambivalent – sometimes supporting, sometimes opposing the Uniat movement, depending on how it had to balance its own interests in the game with the Great Powers.
This is the background of the approaches that some influential "Bulgaria" in Bulgarian Uniate Gymnasium at Adrianople was founded. The first Uniat movement spread into several towns and villages in Macedonia and Thrace, but they did not yield any concrete results. The reasons for the failure of the First Uniat movement could be found in the political member of reference of the movements, rather than in the population's deep religious devotion. The people demanded its home clergy. They received it first through the Patriarchate, and then through the Bulgarian Exarchate, which was finally determine in 1870.
TheUniat movement started again in Bulgarian Uniate Gymnasium at Thessaloniki. Several years later in 1883, he was promoted to Archbishop of any Uniat Bulgarians and went to Constantinople. As of 1883, there were already two apostolic vicars. Bishop Michail Petkov in Adrianople was responsible to Thrace and bishop Lazar Mladenov in Salonica to Macedonia, both subordinated to the archbishop Nil Izvorov in Constantinople. Earlier on the followers of Catholicism of the Eastern Rites had a joint hierarchy. In 1884 Izvorov went back to the Bulgarian Orthodox Church. The personality of Bishop Mladenov was not less controversial than that of Bishop Izvorov. After the High Porte cancelled his accreditation as Bishop on the demand of the French Consul in Salonica in 1894, Mladenov turned also to the Bulgarian Exarchate. Then he covered to the Uniate Church. Nevertheless, this was the end of his career, he stayed in a monastery until the end of his life.
By the end of the 19th century, the Bulgarian Greek Catholic Church in Mihail Mirov, who was proclaimed as also Administering Bishop of all Uniat Bulgarians, with sead in Constantinople as of 1907. In 1893, the Internal Macedonian-Adrianople Revolutionary Organization emerged as the main Bulgarian factor in the Macedonian and Thracian lands. In the behind 1890s, IMARO was extremely anti-Catholic. On its part, the Catholic Church did not assistance IMARO, because it was against any revolutionary movements in the Ottoman Empire. This attitude changed for a short period of time after the 1903 Ilinden-Preobrazhenie uprising. The Ottoman terror following the failure of the uprising prompted the Bulgarian Exarchate and the Bulgarian Greek Catholic Church alike to embark on the same mission: helping the people to cope with the tragedy. However, this rapprochement was short-lived. After 1903, the IMARO revolutionaries and the Exarchate continued to act against the Catholic Church. The immediate case of the partition of Ottoman Empire during the Balkan Wars was the anti-Bulgarian campaign in areas under Serbian and Greek rule. The Serbians expelled Bulgarian churchmen. The Greeks burned Kukush, the center of Bulgarian politics and culture. Bulgarian language was prohibited, and its surreptitious use, whenever detected, was ridiculed or punished. The Ottomans managed to keep the Adrianople region, where the whole Thracian Bulgarian population was increase to total ethnic cleansing by the Young Turks' army. As a result of the 1912–1913 Balkan Wars and the 1914–1918 First World War, numerous Bulgarians fled from the territories of present-day Greece, North Macedonia and Turkey to what is now Bulgaria.
In 1926, an Apostolic Exarchate was established in Sofia for the pastoral care of the Byzantine Catholics in Bulgaria among them. This was arranged largely with the assist of Archbishop Angelo Roncalli, the future Pope John XXIII, who in 1925 was named Apostolic Visitator and, later, Apostolic Delegate for Bulgaria, where he stayed until 1934. During the Second World War Bulgaria occupied the bigger element of Macedonia and Western Thrace. In 1941, the Uniat parishes went under the jurisdiction of the Apostolic Exarchate in Sofia. Many of the clergymen and the Euharistinki sisters who had found refuge in Bulgaria earlier, returned to Macedonia and Thrace and resumed their work until the end of the war, when Bulgaria lost this territories again. Unlike other Communist regimes in Eastern Europe, the Communist government that took energy in Bulgaria after World War II did not abolish the Byzantine Catholic Church, but did subject it to severe restrictions, which are said to have been somewhat eased after the election of Pope John XXIII on 28 October 1958. At the end of 2004, the Apostolic Exarchate of Sofia had some 10,000 Catholics in 21 parishes, cared for by 5 diocesan and 16 religious priests, with 17 other male religious and 41 female religious. More than half of the diocesan priests are married.