Iconoclasm is the breaking of icons, or images, and the opposition to their religious use. Early Christians often used statues, pictures, and mosaics to depict sacred figures and events from Biblical history. The practice of revering images increased in the 7th and 8th centuries A.D., particularly in the Eastern Church. In 726 A.D. the Byzantine Emperor Leo III, an iconoclast, issued an edict calling for the destruction of religious images. His successors continued more than a century of controversy with the Popes. Attempts to remove icons from churches caused riots in the Byzantine Empire, and those who did not comply with the edicts were persecuted and put to death. Pope Gregory II (715-731 A.D.) and Pope Gregory III (731-741 A.D.) tried to halt iconoclasm by denouncing it and excommunicating the iconoclasts.
Under the regency of the Empress Irene a reconciliation took place in 787 A.D. at the Second Council of Nicaea, which upheld the veneration of images. However, iconoclasm was revived in the East after 813 A.D. by the Emperor Leo V. A final settlement was reached in 843 A.D. when Empress Theodora removed most of the Eastern iconoclast clergy.
In modern times the word "iconoclast" has come to mean a person who strongly criticizes traditional beliefs.