In the year 726 C.E., the Byzantine emperor Leo III issued an edict declaring images to be idols, forbidden by Exodus, and ordering all such images in churches to be destroyed. Thus commenced the first wave of Byzantine iconoclasm, which ran its violent course until 787, when the underlying issues were temporarily resolved at the Second Council of Nicaea. In 815, a second great wave of iconoclasm was set off, only to end in 842 when the icons were restored to the churches of the East and the iconoclasts excommunicated.

The iconoclast controversies have long been understood as marking...