In the period of its greatest expansion, in the tenth century, the Syriac Orthodox Church had around 20 metropolitan dioceses and a little over a hundred suffragan dioceses. By the seventeenth century, only 20 dioceses remained, reduced in the twentieth century to 10. The seat of Syriac Orthodox Patriarch of Antioch was at Mardin before the First World War, and thereafter in Deir Zaʿfaran, from 1932 in Homs, and finally from 1959 in Damascus.
Syriac Orthodox Church before the Arab invasions
When the Syriac Orthodox movement began in the sixth century, the Christian world was organised into five patriarchates: Rome, Constantinople, Antioch, Alexandria and Jerusalem. The Syriac Orthodox movement was initially confined to the eastern provinces of the Roman empire, in the territory of the patriarchates of Antioch and Jerusalem. Syriac Orthodox Christians envisaged their church as the legitimate patriarchate of Antioch and appear to have tried to duplicate the hierarchy already existing.
Syriac Orthodox Church under the caliphate
Over a hundred Syriac Orthodox dioceses and around a thousand bishops are attested between the sixth and thirteenth centuries. The main sources for these dioceses and bishops are the lists of Michael the Syrian, compiled in the twelfth century. Many other dioceses and bishops are mentioned in other literary sources, particularly the works of Bar Hebraeus, written in the second half of the thirteenth century. Several bishops not known either to Michael the Syrian or Bar Hebraeus are mentioned in the colophons of surviving West Syriac manuscripts.
Syria
Eight Syriac Orthodox dioceses are known to have existed at various periods before the fourteenth century in southern Syria, in the areas covered by the Chalcedonian province of Phoenicia Libanesia and the southern part of the province of Euphratensis. There was a Syriac Orthodox diocese for Damascus, first attested in the seventh century. The diocese persisted into the fourteenth century and appears to have been one of the few Syriac Orthodox dioceses which continued undisturbed into the fifteenth century and beyond. Emesa (Homs) and Palmyra (Tadmor) also had Syriac Orthodox dioceses. There was an ephemeral Jacobite diocese for the coastal port of Laodicea (Latakia) in the ninth century; and an ephemeral Jacobite diocese for Sadad, a town between Damascus and Homs, in the twelfth century.
There was also a Syriac Orthodox diocese for Heliopolis (Baalbek), attested between the seventh and eleventh centuries; and a diocese for Kfar Tab near Homs, attested in the eleventh and twelfth centuries. No record has survived of Syriac Orthodox bishops in the other towns in Phoenicia Libanesia with known Chalcedonian dioceses (Salamias, Evaria, Iabruda, Abila and Chonochora), though Iabruda certainly had a Syriac Orthodox community. As far as the southern part of the Chalcedonian province of Euphratensis is concerned, a Syriac Orthodox diocese is attested for Sergiopolis (Resafa) in the ninth and tenth centuries.
Nine Syriac Orthodox dioceses are known to have existed at various periods before the fourteenth century in northern Syria. The diocese of Apamea, which was the seat of a metropolitan by the eighth century, is attested between the seventh and tenth centuries; Seleucia Pieria in the eighth and ninth centuries; Berrhoea (Aleppo) between the seventh and late-thirteenth centuries; Beth Balesh between the eighth and eleventh centuries; Cyrrhus between the eighth and eleventh centuries; Qenneshrin between the eighth and tenth centuries; Mabbugh between the ninth and twelfth centuries; Gishra between the eighth and tenth centuries; and Karshena (Gudpaï) in the eleventh and twelfth centuries.
The diocese of Gishra was incorporated into the diocese of Mabbugh during the reign of Athanasius IV (987–1003), and Mabbugh in turn was incorporated into the diocese of Marʿash in the Commagene district in 1155. It is unlikely that any of these dioceses, with the possible exception of Aleppo, persisted beyond the early years of the fourteenth century. Although an almost unbroken succession of bishops of Aleppo is attested from the early years of the sixteenth century onwards, no fourteenth- or fifteenth-century bishops of Aleppo are known. It seems likely that the diocese of Aleppo lapsed after the death of its bishop Mikha'il, attested in 1298, and was only revived at the beginning of the sixteenth century.