The Western Empire falls to Germanic tribes while the Eastern Empire remains. The easterners begin to view the West as a bunch of ignorant, uneducated barbarians.
Acacius, the Bishop of Constantinople, persuades Eastern Emperor Zeno to issue the Henoticon (“Act of Union”) to appease the Monophysites --a doctrinal compromise and a contradiction of Chalcedon, which all the Eastern bishops sign. Pope Felix III excommunicates both Acacius as well as the Patriarchs of Alexandria and Antioch --in essence, excommunicating the entire East!
Latin becomes the official language of the Eastern Empire.
When Pope John I travels to Constantinople and obtains a profession of
orthodox faith from Emperor Justin I --a significant achievement considering
the strength of the Monophysites in the East. Pope John is praised by the
Byzantines as the “successor of Peter,” and is called upon to re-crown
Justin as emperor.
Justinian I is crowned emperor.
Emperor Justinian builds the church of Hagia Sophia.
The nika revolt occurred over the coarse of a week, and was the most violent riot in the history of Constantinople, resulting in half the city being burned and tens of thousands killed.
Justinian's generals reconquer North Africa and Italy from the Vandals and the Ostrogoths.
The Lombard invasion results in the loss of most of Italy from the Byzantines
The climactic Byzantine–Sasanian War commences.
The Arab armies conquered the Levant and Egypt.
In a desperate attempt to re-unify his Christian Empire and
bring the dissident Christians of Egypt, Palestine, and Syria back into the
fold, Emperor Constans II tries to impose the doctrine of Monothelitism on the Empire as a compromise with Monophysitism. The heresy is rejected by the West, but temporarily embraced by the Maronite church in Syria and Lebanon.
After condemning the heresy of Monothelitism at a synod held in Rome, Pope Martin I is arrested by Byzantine troops and taken to Constantinople, where he is publicly abused by the mob and then exiled to Crimea, dying for orthodoxy.
When the Council of Constantinople III condemns Monothelitism, reuniting the Church, the Council of Constantinople III also calls Pope Agatho “the head of the Church”.
The Byzantine city of Carthage in North Africa falls to the Arab invasion.
Rome recognizes Constantinople as a patriarchate. With the two great Eastern seas of Alexandria and Antioch reduced to minor Christian communities by the Muslims, Constantinople remains the only Christian capital in the East.
Pope Gregory III excommunicates the Iconoclasts, infuriating Emperor Leo III, who evidently influenced by Islamic sensibilities which/and promoted the heresy.
It was healed by the Council of Nicaea II, which condemns the Iconoclasts and restores the use of images in Church worship.
Pope Leo III crowns Charlemagne Emperor of the West (A.K.A. Holy Roman Emperor). This act marks the end of Papal dependence on the Eastern Emperor, but the Pope refuses Charlemagne’s pressure to include the “Filioque clause” in the Nicene Creed, so as not to alienate the East.
Charles the Great passes away on January 28, 814 at the age of 72 due to natural causes.
Boris I withdraws his acceptance of the primacy of Rome when Pope Adrian II refuses to make Bulgaria a patriarchate. Bulgaria shifts its allegiance to Constantinople -- a Byzantine political coup, since Constantinople needed to “control” the Bulgarians to protect their northern frontier.
The Byzantine court sends Sts. Cyril and Methodius into the Balkans to convert the pagan Slavs. Though originally part of the Eastern Empire, this region falls into the Pope of
Rome’s Western patriarchate; and Roman Rite missionaries from Germany conflict
with the Byzantines, who are adapting the Liturgy into Slavonic, and thus
achieving more conversions. To get to the bottom of this conflict, the Pope
calls Cyril and Methodius to Rome; and Rome gives its blessing to their
ministry. Cyril and Methodius also recognize the universal primacy of the
Pope of Rome. Thus, the Slavic Balkan kingdoms embrace the Byzantine Rite as
opposed to the Roman Rite --another coup for the court of Constantinople
which, as with Bulgaria, needed to establish religious /cultural ties with
the Slavs so as to safeguard the Empire’s northern frontier.
Photius, the brilliant but illegally-elected Patriarch of Constantinople, conflicts with Pope Nicholas I and Pope Adrian II over his election. He challenges the authority of the Papacy, and criticizes the “Filioque clause.”
When Emperor Basil I calls the 6th Council of Constantinople to remove Photius from office.
The Byzantine Empire deals a string of defeats upon the Arab border emirates and the Abbasid and Fatimid Caliphates, reconquering parts of Armenia, Mesopotamia, Syria and Palestine.
The Bulgarian army is completely defeated at the Battle of Kleidion.
Bulgaria surrenders and is added to the empire. All of the Balkans are incorporated into the Byzantine Empire, with the Danube restored as the imperial frontier to the north.
The West adopts the “Filioque clause” into the Nicene Creed.
With the death of Basil II, the zenith of the Empire's power is passed and the long decline of the Byzantine Empire begins.
Michael Cerularius, Patriarch of Constantinople, launches an anti-Latin campaign. He closes all the Latin churches in Constantinople and attacks the “Filioque clause” and Papal authority, claiming that the Pope has no authority to adopt the Creed. His army enters latin Churches in Constantinople and throws Eucharists into the street.
The split between the Church in Rome and the Church in Constantinople.