1054
July 16 – Cardinal Humbertus, a representative of Pope Leo IX, and Michael Cerularius, Patriarch of Constantinople, decree each other excommunication. Most historians look to this act as the final step in the initiation of the Great Schism between the Roman Catholic and Orthodox Christian Churches. In 1965, those excommunications are cancelled by Pope Paul VI and Patriarch Athenagoras when they meet in the Second Vatican Council. However, to this day each church claims to be the One Holy Catholic and Apostolic Church and each denies the other's right to that name. (See East-West Schism)