Pope Nicholas I
Pope Nicholas I reigned from
858 to
867, and is remembered as a consolidator of Papal authority and power. He refused to grant an annulment to
Lothar II from Theutberga so that Lothar could marry his mistress Waldrada; when a Council pronounced in favor of annulment Nicholas I declared the Council to be deposed, its messengers excommunicated, and its decisions void. Despite pressure from the Carolingians, who laid siege to Rome, his decision held. During his reign, relations with the
Byzantine Empire soured over his support for Ignatius as
Patriarch of Constantinople, who had been removed and
Photius appointed to replace him.