ADMINISTRATIONquered from the Byzantines (see fig. 5),17 With its southern limit formed
by the Jabal Sinjar, it stretched westward to the frontier city and
provincial capital of Nasibin on the Byzantine border. In the late
Sasanian period, this province seems to have been composed of the
districts of Nasibin, Balad, Sinjar, possibly Beth 'Arbhaye, and pos-
sibly the districts of Arzon, Qardo, and Beth Zabhde along the Tigris.
In the course of the Islamic conquest this province, with Nasibin as
its capital, survived fairly intact and became the basis for the region
and administrative unit called the Diyar Rabi'a by the Arabs. During
the conquest this province was subject to invasion from two directions.
In 638 a force under 'Abdullah ibn 'Abdullah ibn '!tban went up the
Tigris to (the province of) Mawsil, crossed the river to Balad, and
went as far as Nasibin, which was taken peacefully and granted the
same terms as the people of Raqqa in Byzantine Mesopotamia.ls A
year or two later, in 639--40, 'Iyad ibn Ghanm, then in the process
of reducing the cities of Byzantine Mesopotamia, sent a force under
Abii Miisa al-Ash'ari which occupied the province of Nasibin. Sinjar
was garrisoned by Muslim troops, and 'Iyad himself is said to have
conquered Balad and to have reached the site of Mawsil. The settle-
ment made by the Muslims in Byzantine Mesopotamia was then ex-
tended to the province of Nasibin where kharaj was imposed on the
lands and on the necks of the inhabitants, and a poll tax of four, five,
or six dznars (L.) apiece was levied in Byzantine gold coins,19 Since
the Muslim army under 'Iyad ibn Ghanm, which conquered this prov-
ince, had come from the direction of Byzantine Mesopotamia, Nasibin
and its districts were henceforth united administratively with the J azira
and were no longer organized as part of Iraq.20
The Diyar Rabi'a appears to have served as an administrative di-
vision of the Jazira from the. time of the Islamic conquest. We are told
that during the caliph ate of 'Umar I (634-44), al-Walid ibn 'Uqba
was 'amil of Rabi'a in the Jazira.^21 As defined by Ibn Khurradadhbih,
the districts (kuwar) of the Diyar Rabi'a included not only those of
Nasibin, Arzan, Ba'arbaya, Balad, Sinjar, Qarda, Bazabda, and Tur
17 Dillemann, Haute Mesopotamie orientale, p. 114; Hoffmann, Persischer M(irtyrer,
pp. 22-24.
18 Tabari, Ta'rtkh, I, 2507.
19 Baladhuri, Futu~, pp. 177, 333; Tabari, Ta'rtkh, I, 2506; Ya'qiibi, Ta'rfkh, 11,
172.
20 Ibn Rustah (A'laq, p. 107) lists Arzan, Qarda, Bazabda, Balad, and Nasibin among
the kuwar of al-Jazira.
21 Tabari, Ta'rfkh, I, 2812.