By this point, the Arabs appeared to the Romans as invincible, and thus, could only hinder themselves. Fortunately for Byzantium, the Arabs began to do just that. The Caliph Uthman ibn Affan was assassinated in Medina. As a result, Ali, the Islamic Prophet Muhammed's son-in law was elected as his successor. However, Muawiya, the governor of Syria who led the Arab fleet against Byzantium, was proclaimed Caliph in Syria, as well. Only when Ali was assassinated in 661 did the civil strife end, much to Byzantium's disappointment.