Secrets of Islam's Success
When Muhammad died, in 632, Islam could boast only semi-stable control over part of the Arabian peninsula. The prophet's territorial gains had been mainly pagan losses. Further expansion required conquest of Christian lands—a task that would prove all too easy, thanks to years of imperial and doctrinal wars.
To Islam's west lay Egypt and the rest of Christian North Africa. Once consolidated under the Roman Empire, by the sixth century the territory was divided between Latin-speaking Berbers in the west and Greek-speaking Byzantines in the east, with a few Baal-worshipers in the south.
Africa's theological divisions ran even deeper. Byzantines upheld the two-faceted definition of Christ's nature affirmed by the Council of Chalcedon in 451, but Egypt's Monophysite ("one nature") Christians, along with churches in Armenia and Syria, vehemently rejected it. African Christianity was also plagued by controversies among catholics, Donatists (who insisted that all other Christians were apostate), Nestorians (who disagreed with both Monophysite and Chalcedonian Christology), and radical desert ascetics.
To Islam's near north and east sprawled the massive, though fading, Persian Sassanid Empire. The Zoroastrian Persians had persecuted Christians severely in the fourth century, judging the new friends of Persia's old enemy, Rome, to be a threat. After a toleration edict in 409, though, the Persians opted to control the church rather than destroy it.
By meddling in ecclesiastical governance, Persia had sent the local church into serious decline by the turn of the seventh century. Conflict between Nestorians, the majority Christian group, and their sworn enemies, Monophysites, hastened the slide.
To the northwest lay the shrinking Byzantine ...