In 753, Emperor Constantine V convened the Synod of Hieria, which declared that images of Jesus misrepresented him and that images of Mary and the saints were idols. The Second Council of Nicaea restored the veneration of icons and ended the first iconoclasm.
The Second Council of Nicaea (recognized as the seventh of the first seven ecumenical councils by both West and East. Orthodox, Catholics, and Old Catholics unanimously) was prompted not by a doctrine about the nature of Jesus but by the iconoclastic controversy. It was the seventh and the last of the councils recognized by both the Catholic and Orthodox Churches and 367 Bishops were present.
This controversy began in the eighth century and gained strength in the eastern lands of the empire. Was it right to make painted or sculptured representations of Jesus and the saints, and direct homage to such images? The defenders of image worship claimed that if Jesus was really a man, it was logical that he could be represented in visible form. When the Jews had been forbidden to make images of God, the reason given was that they “saw no form” of God.
In Jesus, however, God had shown Himself in visible form, and therefore if the making of images was wrong, this was denying the Incarnation. The Monophysite East thought that the humanity of Christ was inseparable from his divinity and the effort to represent “a leptos”, or incomprehensible, was useless. The drawing of Jesus' image was trying to separate his humanity from the divinity. The conflict over images remained as a doctrinal argument until in 726 Leo III (717 -741), known as the “Isaurian” (from Germanicia, Mara) enforced Iconoclasm. The reason for his attack on images is not clear. He may have wanted to insure the support of his army which was mostly recruited from Anatolia where iconoclastic belief was strong, influenced by Judaism and Islam.
His edict enforced the removal of all the icons from churches. The controversy which he began lasted for over a hundred years and contributed to the alienation of the Byzantine Church from that of Rome. The iconoclastic policy of the State continued through the reigns of his successors Constantine V (741-745) and Leo IV (775-780). The destruction of images, icons, lasted until the succession of Irene (780-797) upon her husband's death, as regent for her infant son Constantine VI. Irene was a zealous iconodule and wanted to restore the holy images.
However, much of the army was still iconoclast and she moved with caution. She decided to summon a Second Council of Nicaea. It was held in the church of Saint Sophia (Niceae), which restored ruins still survive. Among other things this council declared that icons deserved reverence (Greek proskynesis) but not adoration (Greek lalreia), which was due to God alone, and condemned the iconoclasts. This statement was confirmed by Pope Adrian I, but partly because of an incompetent translation it was not acceptable generally in the West.
For instance, the two words, proskynesis and lalreia, were equated in translation so it appeared that the council ordered Christians to worship icons in the same way they worshipped God.
This Council completed the split between Rome and Constantinople, which had been heralded by the Fourth Ecumenical Council in Chalcedon (451); the Roman Catholic Church and the Eastern Orthodox Church each going its own way.
The political and economic failures of Irene and her successors caused a reaction in favour of iconoclasm again from 814 until 843. Meanwhile the icons veneration had been maintained by the monks of the Studios Monastery in Constantinople under the leadership of the abbot Theodore, also known as Theodore the Studite, (759-826) whose family, presumably belonged to the iconodule party during the first period of Byzantine Iconoclasm.
The Empress Theodora, who ruled as regent for Michael III, after the death of her iconoclast husband Theophilos (829 - 842) summoned a First Council of Constantinople, which reaffirmed the rulings of the Seventh Ecumenical Councils of 787 and on the first Sunday in Lent 843 restored the icons for the last time with a procession in Hagia Sophia that has become to be known as “the Triumph of Orthodoxy”. Albeit not popular with the majority, the iconoclast emperors were successful soldiers and without them the life of the Byzantine Empire might have been shorter.