The Umayyad Caliphate or Dynasty (661–750 C E) was the first great Islamic empire. Although its leaders were followers of Islam, it was a period marked by religious tolerance, with followers of many other religions given protection as "dhimmis," which, although a form of second-class citizenship, still allowed free practice of religion. This religious tolerance meant that many ancient works of pagan philosophy and science circulated freely in the Arab world in a way they could not in the increasingly intolerant Christian empires of the period.
The Umayyad caliphate was a period in which the sciences flourished. The Arabs preserved and extended the work of Hippocrates and Galen, as well as assimilating other traditions of medicine and practicing both surgery and pharmacology. Mathematicians practiced algebra, geometry, and arithmetic at a more advanced level than in the west, and astronomers continued the Mesopotamian traditions of calculating the movements of the sun and planets for religious purposes (ascertaining the correct direction for prayer) and astrological ones. Although the great philosophical and literary works were slightly later under Abbasid rule, the many traditions of Islamic art and architecture (including the stunning mosaics and elaborate decorative traditions) began under the Umayyads.