Systematic missionary work in Serbia was first undertaken by the Byzantines in the second half of the 9th cent., and by 891 Christianity was the official religion. The attachment of the Serbs to E. Christianity did not become definite until the early 13th cent. An autocephalous Serbian Church was established by St Sava in 1219. In 1346 the head of the Serbian Church assumed the title Patriarch, with his seat at Peć; the Serbian Patriarchate was recognized by Constantinople in 1375. In the Ottoman period the Serbs passed increasingly under Greek ecclesiastical control and the Patriarchate of Peć was suppressed in 1766. The Serbian Church became autocephalous again in 1879, and in 1920 the Patriarchate was restored, its seat being transferred from Péc to Belgrade. A rift in 1992 led to the election of a rival Patriarch in 1996, and there are now two rival hierarchies. The Church of Serbia has always been closely identified with the national aspirations of the people, and in the 1990s it was unable to do more than deplore the violence with which the government pursued its aim of a ‘Greater Serbia’.