I've often mentioned how the Western Latin Church rejected the Nicea II Council of the 8th century, which established the prayer to images in the Greek part of Christianity. They sided with those who maintained that icons have no place in the worship of the one true God. This was the last stand of the doctrine of the Church Fathers, whose position against images is well known. Even as late as the 8th century, those who held to that view included the Emperor himself (!), as well as many of the churches and bishops. Thus from the 8th century on, in the Western church had continued to consistently exclude Nicea II from the list of official councils. This explains why the culture of icons has never taken hold in the West, and why to this day the Western churches do not use icons, even among the Romans. However the Popes were on the pro-icons side (in opposition to the rest of the Western church), and from the 8th century on they sought to overturn its doctrine on this point. It's crucial to recognize that the medieval Popes controlled the monks and the scribes who did all the writing (clerics = clerks), and thus in the 12th century one of the Papal scribes simply included Nicea II among the councils, and there it stayed ever since. Now, today, "seven" is seen as a magical number, and "the seven ecumenical councils" is recited like a magical mantra, when in history it was literally the opposite. People have asked me to provide support for this statement. One of the best descriptions can be found in "A Treatise on the Church of Christ" by William Palmer, from the bottom of the page: https://books.google.com/books?id=24wOAAAAIAAJ&pg=PA189#v=onepage&q&f=false "The Pseudo-Synod of Nicea. Let us now turn to the west. It is a matter of certainty that (with the exception of the Roman see which always supported and approved it,) the churches of the west generally condemned and rejected the synod of Nice as illegitimate... But what is still more remarkable is, that even the Roman pontiffs themselves, though they always received and strenuously defended the synod of Nice, did not for a long time include it in the number of oecumenical synods. In 859, Pope Nicholas I in his reply to a letter of Ado, bishop of Vienne, asking the pallium, requires his assent only to six general councils — omitting that of Nice: and, lest it should be alleged that this arose merely from that Pope's toleration of the error of the Franks who rejected that council, in the year 863 or 866, he held a synod at Rome, and in the decree against Photius there unanimously made, six general councils only are again acknowledged; excluding as before, the synod of Nice. In this case there can be no conceivable reason for such an omission, except that the church of Rome did not at this period reckon it among the general synods. Even in 871, Pope Hadrian, in a letter to the Emperor Charles the Bald, still only speaks of six general councils, though before this time the eighth, (as it has since been styled by the Romans,) had been approved and confirmed by that Pope. At length, however, the church of Rome held the synod of Nice to be the seventh ecumenical synod, as appears from Cardinal Humbert's excommunication of Cerularius, A. D. 1054. The several chronicles of France and Germany during the ninth and following centuries, uniformly speak of it as a “PSEUDO-SYNOD.” The Annales Francorum, written A. D. 808, say, that at the synod of Frankfort, “the PSEUDO-SYNOD OF THE GREEKS, which they falsely called the seventh, and which they had made in order to sanction the adoration of images, was rejected by the bishops.” It is also termed “pseudo-synod” in the Annales Francorum, continued to 814, and in the anonymous life of Charlemagne written after 814; and is condemned in the annals written after 819. Eginhard, in his Annales Francorum, written in 829, says that at Frankfort, “the synod which had been called by the Greeks not only the seventh, but universal, was entirely annulled by all, as of no force; that it might neither be held nor spoken of as universal.” In 824, the Gallican bishops again condemned it at Paris. Hincmar, archbishop of Rheims, about 870, speaks of the “pseudo-synod” of Nice as entirely destroyed and annulled by a general synod in France. Ado, bishop of Vienne, who died 875, in his chronicle speaks of the “pseudo-synod,” which the Greeks call the seventh. Anastasius, librarian of the Roman church, translated the synod of Nice into Latin, when he was at the (so called) “eighth general synod,” A. D. 870; and, in his preface to it, observes that the French did not approve the worship of images. The chronicles of the monastery of S. Bertinus, written after 884, speak of the synod of Constantinople 870, in which that of Nice was approved, and the worship of images authorized, as “ordaining things concerning the adoration of images contrary to the definitions of the orthodox doctors,” &c. The Annales Francorum, written in the abbey of Fulda after the year 900, speak of the synod of Nice as “a pseudo-synod of the Greeks, falsely called the seventh.” Etc. Further on down, he describes how it was surreptitiously snuck in by Papal clerks into the manuscript lists of official councils, in the 11th and 12th centuries; and after that time (until the 16th century) it became a fait accomplit.