"Between Muhammad’s death and the collapse of the Umayyad caliphate in 750, Arab armies appeared everywhere from central Asia, through the Middle East and north Africa, throughout the Visigothic Iberian Peninsula, and even into southern France. They imposed Islamic governments and introduced new ways of living, trading, learning, thinking, building, and praying. The capital of the vast caliphate they established would be Damascus itself, crowned with its Great Mosque—one of the masterpieces of medieval architecture anywhere in the world. In Jerusalem, the Dome of the Rock was built on top of the site of the old Jewish Second Temple—and its gleaming dome became an iconic landmark on that city’s famous skyline. Elsewhere, great new cities like Cairo, Kairouan (Tunisia), and Baghdad grew out of Arab military garrison towns, while other settlements like Merv (Turkmenistan), Samarkand (Uzbekistan), Lisbon, and Córdoba were renewed as major mercantile and trading cities. The caliphate established by the Arab conquests was more than just a new political federation. It was specifically and explicitly a faith empire—more so than the Roman Empire had ever been, even after Constantine’s conversion and Justinian’s reforms; even after a promulgation late in Heraclius’s reign that all Jews in Byzantium were to be forcibly converted to Christianity. Within this caliphate, an old language—Arabic—and a new religion—Islam—were central to the identity of the conquerors and, as time went on, became ever more central to the lives of the conquered. The creation of a global dar al-Islam (abode, or house of Islam) in the seventh and eighth centuries A.D. would have profound consequences for the rest of the Middle Ages, and indeed for the world today. With the exception of Spain and Portugal (and, later, Sicily), almost every major territory that was captured by early medieval Islamic armies retained, and still retains today, an Islamic identity and culture. The spirit of scientific invention and intellectual inquiry that thrived in some of the larger and more cosmopolitan Islamic cities would come to play a key role in the Renaissance of the later Middle Ages."