In the 11th century, the church broke into two: Roman Catholicism and Eastern Orthodox. There were several reasons. The simplest explanation, I guess, was the cross anathemas declared by Michael Cerularius of Constantinople and Pope Leo IX of Rome in 1054 AD based on arguments about authority, and the Bread of the Eucharist, but actually it was the culmination of tensions that started long before.
The general historical order beginning in the 2nd century would be differences that arose over:
a) The Pashcal
c) The Filioque Clause
d) The Bread.
The story did not end there; it actually continued on different fronts until in 1204 AD when the Roman Bishop (Innocent III) called for a 4th Crusade, in which they attacked and sacked Constantinople, conquering the Hagia Sophia.
In my humble opinion, the division all started around 110 to 130 AD when a disagreement (though totally peaceful) arose over the Paschal
festival (called "Easter" many centuries later). The Bishops of the East, allegedly having always followed the instructions of the Apostles, observed "the feast" celebrating His death till He comes (culminating in celebrating the Resurrection on the 1st day of the week following the Passover which the Jews called "first fruits") while the Bishops of Rome had chosen to focus on the "Sunday" as the day of Resurrection.
Now do not misunderstand. The entire Christian church met on the 1st day of each week and broke bread in commemoration of the Resurrection, that was the foundation of the Church, but I am referring specifically to the Paschal
(student of St. John and Bishop of Smyrna) travelled to Rome to meet and discuss the issue with Anicetus who at that time was the Bishop there. Polycarp pointed to the teaching handed down by St. John, but depending on the viewpoint one can see this in the Scriptures as well.
In Luke 22:19 Jesus commands His followers and says, "And he took bread, and gave thanks, and broke it, and gave unto them, saying, This is my body which is given for you: do this in remembrance of me.
" (Emphasis added.)
Later we read in 1 Corinthians 5:7-8, "For even Christ our Passover
is sacrificed for us: Therefore let us keep the feast
, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth. (Emphasis added.)
1 Corinthians 11:23-26 says, "For I have received of the Lord that which also I delivered unto you, that the Lord Jesus the same night in which he was betrayed took bread: And when he had given thanks, he broke it, and said, 'Take, eat: this is my body, which is broken for you: this do in remembrance of me. After the same manner also he took the cup, when he had supped, saying, this cup is the new testament in my blood: this do you, as oft as you drink it, in remembrance of me.' For as often as you eat this bread, and drink this cup, you show the Lord's death till he comes
." (Emphasis added.)
So the Bishops of the East would "keep the feast" (Pashca
from Pesach or Passover) intending to do so "till He come," which would culminate in an all-night vigil till dawn on the 1st day (the concept of Sunday or a day of the Sun was not even in their frame of reference). Anicetus and his companions felt the importance was the resurrection, not His death (and possibly "to keep the feast" was too Jewish). The two agreed each group would do as they believed in good conscience before the Lord, and would not allow the ritualistic difference to be a cause for division (maintaining unity of the Spirit).
After a few generations, this issue came in question again as Churches interacted and teachers and preachers travelled more. Around 190 AD, Victor (Bishop of Rome) claimed sole authority over all the churches, claiming that because Peter was the first Bishop of Rome he had this right. In his decree he commanded that all churches
observe the Pashca
only as Rome did. Eastern bishops rejected his claim of ultimate authority. In 193 AD, Polycrates of Ephesus (a church founded by Paul where both Paul and John had taught, and for a while Mary had resided) protested on the former Bishop's apostolic basis and also refuted Victor's alleged authority over all.
Since the beginning, in each Church founded and taught by an apostle, the bishops always considered themselves autocephalous (equal independent leaders), and in matters where questions arose they would get together and discuss, and by the Scriptures and their traditions they would come to agreement, but none of these (considered to be servants of servants) ever assumed sole authority over all. Even Peter had taught not to lord it over one another as the Gentiles do (1 Peter 5:3). Victor then threw the first historically recorded anathema
, allegedly ex-communicating Polycrates. Irenaeus
and others interceded on Polycrates' behalf against Victor, and the issue for a time was resolved (Eusibius, History of the Church, Vol. 24, 10-11).
The issue of Peter's alleged primacy became a matter of dispute between Rome and the rest of the bishops. Though Peter was in Rome later with Paul, and died there, there is no evidence or indication he was ever the 1st Bishop there. Paul, who only went where no other Apostle had previously been, went to Rome; Priscilla and Aquila were already there fellowshipping with other Christians who regularly met in house churches on the first day of the week. Peter came later. The official 1st Bishop of Rome (appointed by Paul and Peter) was Linus.
Peter, on the other hand, had been a bishop of a church years before coming to Rome (he arrived in Rome around 60 AD). In fact, he was their first bishop. It is a matter of history that Peter was actually the first Bishop of Antioch (in Syria) around 50 AD for around two years, where he taught and appointed Evodius, who then appointed Ignatius (a student of St. John) in 100 AD. All the apostles (including Peter) looked to Jerusalem as the true mother church, if one wishes to use such a term, and saw James (the brother of our Lord) as the actual first Bishop of the Church ever. Even Peter was under the general authority of James until James was martyred (though, as I indicated, real authority was in the council not in the final word of one man).
In time, by the late 2nd and early 3rd centuries, the Church recognized five primary centers, and their bishops were looked up to as sources of true guidance. These five autocephalous Patriarchates were Jerusalem, Antioch, Ephesus, Rome, and Alexandria in Egypt.
Politically/secularly, Rome was still the capital of the Empire — and then came Constantine. Soon after he became emperor he moved the capital of the Empire to Turkey, naming Byzantium as the new capital and renaming it Constantinople (after himself). This made many Romans (and Roman bishops who, after Victor, assumed authority over all others) very angry. The Council of Nicea was ordered by the Emperor to foster unity, and the original Nicene Creed
was formed (around 325-330 AD).
Shortly after, there was a new dispute (called the Filioque). The original creed says, "I believe in the Holy Spirit, the Lord, the giver of life, who proceeds from the Father. Who with the Father and the Son is adored and glorified." In this case, because Jesus can be said and shown to also direct and send the Spirit they insisted on changing it to say, "I believe in the Holy Spirit, the Lord, the giver of life, who proceeds from the Father, AND THE SON. Who with the Father and the Son is adored and glorified." Whether it was just because it was Rome or because they relied on what had been agreed to by all
the bishops at the Council, the bishops of the East now enjoying their place in relation to the political authority, refused to change it. As you can see the wedge widening even as far back as this.
Later still (a few centuries) a question of the bread to be used at the Pashca
arose (and in communion weekly) for allegedly (they still claim this) the East had always used a consecrated loaf of leavened bread (for Christ the bread of life had now risen and His Spirit now leavens the whole lump, ie., the Church). But Rome and other centers under their See (North Africa, France, and some of the Balkan states) maintained that this bread should be unleavened according to Scripture and tradition.
So you can see that by the time of 1054 AD the divisions were manifold, and by this time they were quite irresolvable; neither side was going to budge, and cross anathemas broke "Communion" on what seemed to be on a permanent basis. But the true absolute break up (in my opinion) was finalized with the attack of 1204 AD. Baldwin of Flanders entered the Hagia Sophia and declared himself Baldwin I emperor of the Latin Empire. The split was sealed.