While both Christianity and Islam claimed to be universal religions, and both expanded their influence and control greatly, they were also both beset by tensions. From the expansion of Christianity after the fall of Rome, multiple Christianities emerged, helping to connect, but also define and delineate, the Byzantine Empire, the Christian worlds of Africa and Asia, and the western part of the former Roman Empire. Competing with this growth and development in Christianity, Islam emerged on the Arabian peninsula, and within a short period of time, started to expand and challenge all areas of Christianity. While both religions were used as a connection, they both suffered divisions and splits that prevented either from being as universal as they would have liked. While they did have success in reaching new frontiers, as illustrated by Christianity in the Counterpoint of this chapter, eventually bringing the Norse Viking rulers under the Christian church’s authority and ending the Viking menace, both Christianity and Islam eventually fractured into competing religious traditions and a multitude of states.