Pope Gregory IV

Pope Gregory IV (Latin: Gregorius IV; died 25 January 844) was the bishop of Rome and leader of the Papal States from October 827 to his death on 25 January 844. His pontificate was notable for the papacy’s attempts to intervene in the quarrels between Emperor Louis the Pious and his sons. It also saw the breakup of the Carolingian Empire in 843.

Source: Wikipedia — https://en.wikipedia.org/wiki/Pope_Gregory_IV