Constantine V (Constantine Copronymus), 718–75, Byzantine emperor (741–75), son and successor of Leo III. An able general and administrator, he fought successfully against the Arabs, Slavs, and Bulgars, improved the water supply of Constantinople, forcibly resettled the city after a great plague, and continued his father's financial and religious policies. In 754 he summoned a synod at Constantinople, which sustained iconoclasm. He rigidly enforced a decree forbidding the use of images in worship, and he opposed monasticism. A serious result of this policy was the loss of Rome and, ultimately, of Italy to the Byzantines. Pope Zacharias broke with Constantine, and Pope Stephen II placed Rome under the protection of Pepin the Short. Constantine was succeeded by his son Leo IV.
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