Khvarvaran

Khvārvarān, was a military quarter of the Sasanian Empire. Intensive irrigation agriculture of the lower Tigris and Euphrates and of tributaries such as the Diyala and Karun formed the main resource base of the Sassanid monarchy.

The Arabic term Iraq was not used at this time; in the mid-6th century the Iranian Empire under Sasanian dynasty was divided by Khosrow I into four quarters, of which the western one, called Khvārvarān, included most of modern Iraq, and subdivided to provinces of Meshan, Asuristan, Adiabene and Media. The term Iraq is widely used in the medieval Arabic sources for the area in the centre and south of the modern republic as a geographic rather than a political term, implying no precise boundaries.

The area of modern Iraq north of Tikrit was known in Muslim times as Al-Jazirah, which means "The Island" and refers to the "island" between the Tigris and Euphrates rivers. To the south and west lay the Arabian deserts, inhabited largely by Arab tribesmen who occasionally acknowledged the overlordship of the Sasanian Emperors.

Until 602 the desert frontier of greater Iran had been guarded by the Lakhmid kings of Al-Hira, who were themselves Arabs but who ruled a settled buffer state. In that year Shahanshah Khosrow II Aparviz rashly abolished the Lakhmid kingdom and laid the frontier open to nomad incursions. Farther north the western quarter was bounded by the Byzantine Empire. The frontier more or less followed the modern Syria-Iraq border and continued northward into modern Turkey, leaving Nisibis (modern Nusaybin) as the Sasanian frontier fortress while the Byzantines held Dara and nearby Amida (modern Diyarbakır).

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