Gregorian Reform
In the period from 1050 until 1080, the Gregorian Reform movement developed increasingly more assertive policies, eager to increase its power and influence. This prompted conflict with eastern Christians rooted in the doctrine of papal supremacy. The Eastern church viewed the pope as only one of the five patriarchs of the Church, alongside the Patriarchates of Alexandria, Antioch, Constantinople and Jerusalem. In 1054 differences in custom, creed and practice spurred Pope Leo IX to send a legation to the Patriarch of Constantinople, which ended in mutual excommunication and an East–West Schism.