In the West in the eighth century, barbarian tribes in northern Europe continued to be converted to Christianity. The greatest missionary in this time was Saint Boniface, the Apostle to Germany (680–754). Working on behalf of the Roman Church, he eventually missionized much of northern Germany, and reformed the whole Frankish Church along Roman lines.
During this century the Roman Church turned away from the Byzantine Empire for support, allying itself instead with the newly emerging dynasty of the Franks. This northern tribe, which gave their name to the nation of France, was led by three remarkable leaders in the eighth century: Charles Martel (r. 723–741), who led the army that stopped the advance of the Arabs in western Europe at the famous Battle of Poitiers in 732; Pepin III the Short (r. 741–768), who gave the Roman Church vast tracts of land in central Italy in return for its favor and support; and especially Charlemagne (Charles the Great) (r. 768–814), who was anointed and crowned as Holy Roman Emperor by Pope Leo III on Christmas Day in the year 800.
Ever since Emperor Constantine the Great had permanently moved the imperial capital from Rome to Constantinople, the Roman Church had felt somehow abandoned, if not betrayed. Then it felt threatened when Constantinople began claiming, at the Second Ecumenical Council in 381, to be the “New Rome.” Such feelings only increased with the fall of Rome to the barbarians in 476. Ever since Pope Saint Gregory the Great (r. 590–604) had negotiated a separate peace with the Lombards, the Roman Church had been operating basically independently from Byzantium, fending for itself. When Iconoclasm broke out in the East, the Papacy was given another reason to distrust the Byzantines.
However, in turning to the Franks for protection and support, the Roman Church opened itself to foreign influences which would alienate the two halves of Christendom much further from each other. Three of the most important of these developments were the large tracts of land given to the Church by King Pepin III—the Papal States—that the Papacy would rule administratively as an independent temporal power up until the 19th century; the acquiring of a certain militaristic spirit that would lead to the Crusades, with some Popes even leading armies in battle; and the eventual acceptance of the addition of the filioque in the Nicene Creed, which to this day, along with the dogma of papal infallibility, is probably the single greatest theological difference between Roman Catholicism and Orthodoxy.
The Carolingian Renaissance
Through his conquests in France, Germany, Spain, and modern day Hungary, Charlemagne created what would be the largest empire in Europe from the fall of Rome in 476 until the time of Napoleon. From his capital in Aachen, he actively promoted higher learning through his patronage of the many scholars at his palace and the remarkable library there. He invited Alcuin (c. 740–804), a prodigious scholar and able representative of the Christian culture of Northumbria, England, to join his court in 781; this remarkable churchman of wide-ranging interests did much to enrich the flowering of learning and refined culture in this period in the West.
Charlemagne took a lively interest in ecclesiastical affairs. He called a series of sixteen Church councils all held in Frankfurt, Germany, and he promoted various reforms in the Frankish Church, including liturgical standardization based on Roman practices.
In 792 Charlemagne sent his Carolingian Books (Libri Carolini) to Pope Hadrian I (r. 772–795), which attacked not only the Iconoclastic Council of 754 for outlawing the icons, but also the Council of Nicea of 787 for allowing excessive reverence for the icons. This charge was apparently partly based on a faulty Latin translation of the decree of that council which did not properly distinguish between the veneration (proskynesis; veneratio in Latin) of the icons, and the worship, or adoration, given to God alone (latreia; adoratio in Latin).
A big reason for Charlemagne’s attack against the Eastern Church was to discredit the Eastern empire and its emperor so that he himself could be recognized as the sole ruler in Christendom. In his vision of the new Holy Roman Empire Charlemagne wanted to include all of the East together with all of the West in what he believed was the legitimate continuation of the ancient Roman Empire, overriding the fact that the Roman Empire still existed in the eastern half of the ancient Empire.
Charlemagne also played a major role in the sad story of the addition of the filioque into the Nicene Creed. He had grown up with the filioque, and urged the Roman Church to accept it. Pope Leo III (r. 795–816) resisted its imposition in Rome to such an extent that he had the original Creed engraved on silver tablets prominently displayed in Saint Peter’s Cathedral in Rome. However, he allowed the Frankish Church to use it. Eventually, the Roman Church yielded to the Germanic pressure and accepted the filioque—using it for the first time in public worship in 1014. The Byzantine Church actually had dropped the pope’s name from the diptychs five years before, when Pope Sergius wrote a confession of faith that included the filioque. This was the first specific step towards the Great Schism of 1054.