723 (emir Yazid's edict) – 726–730 (Leo III's first edicts) – 754 (council of Hieria) – 787 (Seventh Ecumenical Council at Nicaea)

The Iconoclast controversy and the Seventh Ecumenical Council (Second Nicaea, 787)

Around 723 the Muslim emir Yazid ordered the destruction of all icons in his territories. According to one source, this example influenced Emperor Leo III the Isaurian. In 726 Leo issued his first edict against icons, and in 730 a second, unconditional one, deposing the resisting Patriarch Germanus. Pope Gregory II responded with anathema and convened a Roman council in defense of icons (727). Italy temporarily withdrew its allegiance to the emperor.

Leo's successor, Constantine V Copronymus, took iconoclasm to an extreme. In 754 he convened a council of 338 bishops at Hieria, without representatives from Rome or the Eastern patriarchates. The council declared icon veneration idolatry and the Eucharist the only true image of Christ. It anathematized the defenders of icons, including John of Damascus. Savage persecution of icon-venerating monks followed, among them Stephen the New, along with the destruction of images, books, and relics.

The doctrine and practice of icon veneration were defended by theologians such as John of Damascus and Leontius of Neapolis, and later by Patriarch Nicephorus and Theodore the Studite.

Persecution eased for a time under Leo IV. Then the regent Irene, the emperor's widow, convened the Seventh Ecumenical Council. A first attempt at Constantinople in 786 was disrupted, and in 787 the council met at Nicaea. Patriarch Tarasius presided, and legates of Pope Adrian I were present. The council solemnly refuted the definition of 754. It decreed that icons of Christ, the Theotokos, angels, and saints deserve reverent veneration (dulia) but not the worship (latria) due to God alone.

In the Latin West the council's decisions were received ambiguously because of a faulty translation. The Libri Carolini at Charlemagne's court rejected "superstitious worship" of icons, though without approving their destruction. The Council of Frankfurt in 794 formally rejected Nicaea's decisions.