 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.Pope Alexander II developed recruitment systems via oaths for military resourcing that Gregory VII further extended across Europe.