Foundation and construction Damascus was captured by Muslim Arab forces led by Khalid ibn al-Walid in 634. In 661, the Islamic Caliphate came under the rule of the Umayyad dynasty, which chose Damascus to be the administrative capital of the Muslim world. The Byzantine cathedral had remained in use by the local Christians, but a prayer room (musalla) for Muslims was constructed on the southeastern part of the building. The musalla did not have the capacity to house the rapidly growing number of Muslim worshippers in Damascus. The city otherwise lacked sufficient free space for a large congregational mosque. The sixth Umayyad caliph, al-Walid I (r. 705–715), resolved to construct such a mosque on the site of the cathedral in 706. Al-Walid personally supervised the project and had most of the cathedral, including the musalla, demolished. The construction of the mosque completely altered the layout of the building, though it preserved the outer walls of the temenos (sanctuary or inner enclosure) of the Roman-era temple. While the church (and the temples before it) had the main building located at the centre of the rectangular enclosure, the mosque's prayer hall is placed against its south wall. The architect recycled the columns and arcades of the church, dismantling and repositioning them in the new structure. Professor Alain George has re-examined the architecture and design of this first mosque on the site via three previously untranslated poems and the descriptions of medieval scholars. Besides its use as a large congregational mosque for the Damascenes, the new house of worship was meant as a tribute to the city. In response to Christian protest at the move, al-Walid ordered all the other confiscated churches in the city to be returned to the Christians as compensation. The mosque was completed in 711, or in 715, shortly after al-Walid's death, by his successor, Sulayman ibn Abd al-Malik (). According to 10th-century Persian historian Ibn al-Faqih, somewhere between 600,000 and 1,000,000 gold dinars were spent on the project. The historian Khalid Yahya Blankinship notes that the field army of Damascus, numbering some 45,000 soldiers, were taxed a quarter of their salaries for nine years to pay for its construction. Coptic craftsmen as well as Persian, Indian, Greek, and Moroccan laborers provided the bulk of the labor force which consisted of 12,000 people. Layout design The plan of the new mosque was innovative and highly influential in the history