In 1054, the church was split between East and West. Because of the
invasions of the Balkan, the churches was somewhat separated. Also, the
churches spoke different languages, in the West spoke Latin and Greek in the
East, which made communication harder.
Michael Cerelarius tried to
shut down the Latin Church. Then Pope Leo IX countered by sending one
of his cardinals to insist that Constantinople submit to Rome.
The schism did not occur because of two hotheaded leaders, there were a lot of different arguments that led the split.
Saw the Pope as the last Apostolic See
The Pope was free to run the church in the West
Saw Pope as "First among equals"
His position was not supposed to govern the Eastern Church as Leo tried to claim