Primacy in the Church from Vatican I to Vatican II

The primacy of the bishop of Rome, the pope, as it was finally shaped in the Middle Ages and later defined by Vatican I and II has been one of the thorniest issues in the history of the Western and Eastern Churches. This issue was a primary cause of the division between the two Churches and the events that followed the schism of 1054: the sack of Constantinople by the crusaders in 1204, the appointment by Pope Innocent III of a Latin patriarch of Constantinople, and the establishment of Uniatism