designated the actual borderlands, came to mean "boundaries", employed in phrases like Thughūr al-Islām (, "Boundary of Islam") or Thughūr al-Rūmīya (, "Boundary of the Rūm"). This process was marked by a gradual consolidation of the previously deserted zone and its transformation into a settled and fortified borderland, especially after the Byzantines abandoned Cilicia during the reign of Caliph Abd al-Malik (). The Muslims began to move into the area, reoccupying and repairing the abandoned towns and forts. The process began under the Umayyads, but intensified under the first Abbasids, especially during the rule of Harun al-Rashid (). Thus a line of forts was gradually established, stretching from Tarsus (Ar. Ṭarsūs) on the Mediterranean coast to Malatya (Ar. Malaṭiyā, Gr. Melitene) and Kamacha (Ar. Ḥiṣn Kamkh) on the upper course of the Euphrates. These were located at strategic choke points, located at the intersections of major roads or at the mouths of important passes. Administrative organization and settlements The entire frontier zone was initially part of the jund (one of the military administrative divisions into which Muslim Syria was divided) of Homs. After 680 it formed part of the new jund of Qinnasrin (Gr. Chalkis), until Harun al-Rashid established a separate jund al-ʿAwāṣim () in 786, covering the entire region from the Byzantine border in the north and west to the Euphrates in the east and a line running south of Antioch (Ar. Anṭākiya), Aleppo (Ar. Ḥalab, Gr. Berroia) and Manbij (Gr. Hierapolis). Manbij and later Antioch were the new province's capitals. The al-ʿAwāṣim proper served as the second defensive line behind the Thughūr, stretching across northern Syria and comprising the towns of Baghras, Bayās, Dulūk (Gr. Doliche or Telouch), Alexandretta (Ar. Iskandarīya), Cyrrhus (Ar. Qūrus), Ra'bān and Tīzīn. The Thughūr, the actual frontier zone, was divided into the Cilician or Syrian (al-Thughūr al-Sha'mīya, ) and the Jaziran or Mesopotamian (al-Thughūr al-Jazīrīya, ) sectors, roughly separated by the Amanus mountains. There was no overall governor or administrative centre for the Thughūr, although Tarsus and Malatya emerged as the most important towns in Cilicia and the Mesopotamian sector respectively. The towns of the Thughūr came variously under the administrative control of the jund al-ʿAwāṣim or functioned as separate districts; the situation is complicated by the fact that by the 10th century, the terms Thughūr and al-ʿAwāṣim were often used interchangeably in the sources. In addition, from the early 10th century, with