In Christianity, the theory that the venerations of, or through, icons is a wrong, or even illegal religious practice.
An icon in the Christian context could show both holy people of Christian history as well as Jesus, his family or the earliest Christians.
Among the most important examples of Christian iconoclasm was with Byzantine Emperor Leo 3, who in 730 ordered the veneration of Christian icons prohibited throughout the empire. The background for his decision is unclear, but it has often been suggested that he had been influenced by Muslim ideas (see Muslim iconoclasm). He was harsh in the execution of this prohibition, and when not receiving support from the Pope in Rome, he cut off the church's financial sources. He would became excommunicated by the church for this.
For about 50 years through the 8th century, icons were prohibited in the Byzantine Empire. The conflict came to an end in 843, 113 years after Leo 3 formulated his prohibition.
726: Byzantine Emperor Leo 3 speaks out against the veneration of icons among Christians.
730: Leo 3 prohibits Christian icons, and orders the destruction of sacred imagery in churches.
754 February: Byzantine Emperor Constantine 5, son of Leo 3, conveys a synod at Hieria attended only by bishops sympathetic to his Iconoclast line. Constantine uses the decisions here to continue his programme to destroy icon worship.
787: Byzantine Empress Irene summons the Second Council of Nicaea, in which the veneration of icons is reestablished.
815 March: Byzantine Emperor Leo 5 convokes a synod at Constantinople that reimposes iconoclast decrees.
832: Byzantine Emperor Theophilus issues an edict forbidding the veneration of icons, and launches a brutal campaign to stop this practice throughout the empire.
843: Byzantine Emperor Michael 3 allows the veneration of icons. This became the end of this conflict.