territory, forming part of the frontier theme of Mesopotamia, which straddled the Mouzouron range. Eastern Anzitene wasn't taken until 937, and then Arsamosata was besieged from 937 to 939. The Byzantines probably expanded the fortifications at Harput around this time. From this point on, Harput became the main center in Anzitene. Over the next 10 years, the Byzantines continued to expand further east so that by 950, the frontier was well to the east of Anzitene. However, Anzitene vulnerable to attack from across the Armenian Taurus to the south. In 956, the Hamdanid ruler of Aleppo, Sayf al-Dawla, led that exact type of attack into Anzitene. This is one of his most famous campaigns, and the "remarkably detailed" Arabic prose account of it provides a major source about medieval Anzitene and its settlement patterns. This account is found in some manuscripts preceding al-Mutanabbi's two poems about the campaign and probably is based on, or directly copied from, an official Hamdanid bulletin sent out by Sayf al-Dawla and/or his military staff who may have recorded the campaign. The population of Anzitene appears to have declined between the 6th and 10th centuries. Tadım, the late Roman capital of Anzitene, had shrank and retreated to a more defensible location. Harput also appears to have done the same. The only exception to this trend was Hūrī, which seems to have grown from a village into a town. Part of the reason for this decline may have been because of a movement of population northwards into Sophene. What likely happened is that during the Arab invasions, many people left the "open, exposed settlements" on the Anzitene plain for better-protected places in Sophene. As a "fissured limestone country" protected on the south by the Arsanias river, Sophene was better positioned to shield residents from raids and invasions. A local population shift also took place within Anzitene, as the people who remained in the district left the open and exposed settlements on the plains for more elevated sites that offered protection. However, there is no evidence that an internal migration took place from the plains to the highlands of western Anzitene. In contrast to Sophene, whose valleys were small but had rich soil for agriculture, the western Anzitene highlands are poorly suited to support large towns. Meanwhile, the threat of the Byzantines to the west prompted the Arabs to invest in fortifying the northern and western highlands