The Diocese of the East, also called the Diocese of Oriens, (Latin: Dioecesis Orientis; Greek: Διοίκησις Ἑῴα) was a diocese of the later Roman Empire, incorporating the provinces of the western Middle East, between the Mediterranean Sea and Mesopotamia. During late Antiquity, it was one of the major commercial, agricultural, religious and intellectual areas of the empire, and its strategic location facing the Sassanid Empire and the nomadic tribes gave it exceptional military importance.[1]
In 535, as part of his administrative reforms, Justinian I abolished the diocese, and the comes Orientis became the provincial governor of Syria I, while retaining his previous rank of vir spectabilis and his salary.[3]
The entire area of the former diocese came under Sassanid Persian occupation in the 610s and 620s, during the Byzantine–Sassanid War of 602–628. Shortly after the Byzantine victory in the war and the recovery of the region, it was again lost, this time permanently except Cilicia and most of the Levantine coasts later reconquered, to the Muslim conquests: by the 640s, Cilicia formed the border (Al-Awasim) between Byzantium and the new Arab Rashidun Caliphate and its successors, while Cyprus became a disputed territory. From the old provinces of the Diocese of the East, only Isauria and parts of the two Cilicias remained under Byzantine rule, grouped under the new Anatolic Theme.[2]
^ abcGiftopoulou, Sofia (2005). "Diocese of Oriens (Byzantium)". Encyclopaedia of the Hellenic World, Asia Minor. Foundation of the Hellenic World. Archived from the original on 10 June 2015. Retrieved 14 November 2013.
^Bury, John Bagnell (1923). History of the Later Roman Empire: From the Death of Theodosius I to the Death of Justinian, Vol. II. London: MacMillan & Co. p. 339. ISBN0-486-20399-9.
As found in the Notitia Dignitatum. Provincial administration reformed and dioceses established by Diocletian, c. 293. Permanent praetorian prefectures established after the death of Constantine I. Empire permanently partitioned after 395. Exarchates of Ravenna and Africa established after 584. After massive territorial losses in the 7th century, the remaining provinces were superseded by the theme system in c. 640–660, although in Asia Minor and parts of Greece they survived under the themes until the early 9th century.