Q. 1. Can you tell me, what is the "Iconoclasm" heresy?
A. 1. The "Iconoclasm" heresy is the belief that icons are idols and they should all be destroyed.
From the later part of the seventh century, some parts of the Greek Church reacted against the veneration of icons. In 726 A.D., Emperor Leo III ordered the destruction of all the Church icons and persecuted those who refused to participate . The policy continued under his successors until around 780 A.D. Later Leo V launched a second attempt which continued until the death of emperor Theophilus in 842 A.D.
"Iconoclasm" was condemned at the Second Council of Nicaea in 787 A.D. at which time the veneration of icons was regulated.