The Second Council of Nicaea was prompted not by a doctrine about the nature of Jesus but by the iconoclastic controversy. It is the seventh and the last of the councils which were recognized by both the Catholic and Orthodox Churches.
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 (Ot 4: 12) had been 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 the aleptos, 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 -41), known as the 'Isaurian' (from Germanicia, Maraž) 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 (741-45) and Leo IV (775-80). The destruction of images, eikons, lasted until the succession of Irene (780-97) 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 St. Sophia, whose 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. With this council the division between Rome and Constantinople, which had been stimulated by the Fourth Ecumenical Councils in Chalcedon (451) became complete, 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 favor of iconoclasm again from 814 until 843. The iconophile cause was meanwhile being maintained by the monks of the monastery of Studios at Constantinople under their abbot Theodore (759-826).
The empress Theodora, who ruled as regent for Michael III, after the death of her iconoclast husband Theophilos (829-42) 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 St. Sophia that has come to be known as 'the Triumph of Orthodoxy.' Although not popular with the multitude the iconoclast emperors were successful soldiers and without them the life of the Byzantine empire might have been shorter.