“ On the proclamation of Ali as the successor of Othman in 656, Moawiyah revolted, and with the aid of the gifted Amr ibn al-Asi attempted to make himself Caliph. He was defeated in several battles by Ali, who, however, was prevented by domestic rebellion and foreign war from completely crushing his rival. Moawiyah was proclaimed Caliph at Damascus, 657, and after the assassination of Ali in 661 he succeeded in speedily reducing the rest of the Empire to submission. ”