When the first Arab invaders appeared in eastern Transcaucasia in the seventh century, the Caucasus was a borderland between the nomadic world to the north and the old sedentary world to the south, and between the Greek civilization in the West and the Iranian world in the East. It had a highly sophisticated urban civilization where several world religions, including Judaism, Manichaeism, Zoroastrianism, and Christianity, were already well entrenched. Among the Christians, the Georgians and Alans were Orthodox, and the Armenians and Albanians were monophysites. Unlike Central Asia, which has been characterized by religious tolerance, the Caucasus for centuries has been the fighting ground for three great monotheistic religions—Christianity, Judaism, and Islam.

Islam in the Caucasus

The spread of Islam was inhibited by powerful political rivals who reinforced religious rivalries. The Turkic Khazar...