Barely had Christian civilization in the West begun to struggle out of the ruins of the Roman empire when a lethal new threat confronted it. Islam, a religion created by the prophet Muhammad, burst from Arabia, taking by conquest half of Christendom, from Iran to the Atlantic coast of Africa and northward into Spain. Across the prophetś vast domain Christians were forbidden on pain of death to preach the Gospel, ride horses, build tall churches or ring church bells. Facing relentless discrimination, many conquered Christians, and eventually most, converted to Islam, and were prevented on pain of death from switching back. Christendom was now confined to Europe, defended by the armies of Byzantium in the East and the ferocity of the Franks in the West. Here, however, the faith continued to grow, preaching the love and mercy of God and slowly creating order from chaos.