The birth of Islam is marked by the first revelation conveyed to the Prophet Muhammad by God (in Arabic, Allah), which occurred in the seventh century near the city of Mecca on the Arabian Peninsula. Islam emerged in a polytheistic environment; although there were notable Jewish and Christian communities, most people living on the Arabian Peninsula believed in multiple gods. In contrast, the fundamental tenet of Islam was monotheism—the belief in one God alone. What began as a religious movement soon took on a political dimension and Islam spread quickly throughout the Middle and Near East. The fall of the Sasanian empire in Persia and Byzantium's weakening control of its eastern territories in the seventh century provided fertile ground for this expansion, and within a hundred years of the Prophet's death the new leaders of the Islamic community (umma), the caliphs, controlled lands reaching from Spain to present-day Pakistan. The spread of the faith stimulated new architecture and the production of other arts in territories with rich and well-established cultural and artistic traditions. Mosques were built for growing Muslim communities and religious texts about Islamic belief and practice were written and decorated. Works that functioned in or responded to Islamic religious life continued to be produced over the centuries in every region in which Islam is practiced. This unit examines such works and provides an introduction to the beliefs and early history of Islam.