The break in the unity of the Christian Church came in 16th century with the rise of Protestanism. The Protestants rejected the authority of the Pope. The essence of Protestanism is the acceptance by the individual Christian of his direct responsibility to God rather than to the Church.
The leader of the Protestant Reformation in Germany was Martin Luther. He found his own theology which emphasised the deity of Christ, the utter depravity of human nature as a result of the fall of Adam and inherited guilt and salvation by faith in the atoning sacrifice of Christ.
Like the Catholics, the Protestants believe in the theory of trans-bstantiation. The modern Lutherian Church is most active in Germany, Denmark, Iceland, Norway, Sweden and Finland, where it is the established state Church and in the United States.
England became Protestant under Henry VIII by which the King of England became the head of the Church of England in place of the Pope. The authority of the Pope got abrogated and the marriage of the clergy was allowed.