I. History and Religious Demography
The Bulgarian state was founded in 681 C.E. Until the mid-ninth century, the population was pagan, with two different polytheistic strands: the Bulgars or proto-Bulgarians (of Turkic origin), and the Slays. In 864, by a decree of Prince Boris I, Christianity was adopted from Byzantium and proclaimed as the state religion. In 1396, the Ottoman Turks, who had come to the Balkans half a century before, conquered Bulgaria and ruled it for 482 years as part of the Ottoman Empire. Bulgaria's independence was restored in 1878 as a result of a war between the Russian and Ottoman Empires. The five-century presence of Muslim Turks, a remnant of whom continue to live in Bulgaria today, as well as the Islamization of parts of the Christian population, make Islam the second largest faith in Bulgaria today. In the last third of the nineteenth century, Congregationalists, Methodists, and Baptists came to Bulgaria and attracted adherents. Roman Catholicism sought to enter Bulgaria as early as the seventeenth century, but Ca tholic missionaries became especially active and achieved some success only in the 1850's and the 1860's. Pentecostals arrived in Bulgaria in the early twentieth century.
The Constitution of 1878 proclaimed Eastern Orthodoxy the official religion in the Princedom of Bulgaria, and the ruling prince (king, after 1908) was obliged to adopt Orthodoxy as his religion. Other denominations, however, enjoyed a large degree of autonomy. The church was not entirely separated from the state. Such important civil legal institutions as marriage and divorce were the prerogative of the churches. Marriage was valid only if concluded according to the requirements of one's religious rite, and only the ecclesiastical courts had the right to announce divorces. In the public schools religious instruction was mandatory, and students from non-Orthodox families could study their parents' religion. Priests served as military chaplains in the army.
After a coup d'etat in September, 1944, the Communist Party came to power, supported militarily, politically, and economically by the U.S.S.R. Before the Paris peace treaty of 1947,  Soviet troops were dislocated in the country. By a referendum of September 15, 1946,  Bulgaria became a republic, and the Constitution of December, 1947, introduced a complete separation of church and state. Ecclesiastical marriage lost its legal validity; only civil marriages were now valid. Divorces were taken out of the church's jurisdiction, and only civil courts were allowed to announce them. Religious instruction was deleted from the curricula of public schools (private schools were abolished in 1946-48), and the schools became instruments of atheistic propaganda. The military chaplaincy was abolished. Massive repression against the clergy began, with Protestants and Catholics primarily affected. After November 10, 1989, a process of democratic change started in Bulgaria as communism collapsed throughout Eastern Euro pe.
The last census, on December 4, 1992, put the population of Bulgaria at 8,487,317. Censuses taken between 1944 and 1992 did not collect data on religious affiliations of citizens, so reliable data on this matter is available only in the 1992 census. It showed the following distribution of people in Bulgaria by religion: 
Eastern Orthodox 7,274,592 85.71%
Muslim 1,110,295 13.08%
Catholic 53,074 0.62%
Protestant 21,878 0.26%
Armenian Gregorian 9,672 0.11%
Jewish 2,580 0.03%
other 6,430 0.08%
Sunnis are the largest group among Muslims, numbering 1,026,758 or 92.5% of the total Muslim population, while Shiites number 83,537 or 7.5%. According to the census there were 315 persons who defined themselves as Dunovists.  The data on the distribution of people by religion and by mother tongue show that Bulgarian is the mother tongue for 171,000 Muslims, or 15. …