Pope Gregory IV was the bishop of Rome and ruler of the Papal States from October 827 to his death. 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.
Miniature of Pope Gregory IV (c. 840)
Gregory IV (in the middle) receives a book from Rabanus Maurus (on the right)
Division of the Carolingian Empire by the Treaty of Verdun
The interior of St Mark’s Basilica in Rome, including the Byzantine mosaics commissioned by Gregory IV
Louis the Pious, also called the Fair and the Debonaire, was King of the Franks and co-emperor with his father, Charlemagne, from 813. He was also King of Aquitaine from 781. As the only surviving son of Charlemagne and Hildegard, he became the sole ruler of the Franks after his father's death in 814, a position that he held until his death except from November 833 to March 834, when he was deposed.
Louis the Pious, contemporary depiction from 826 as a miles Christi (soldier of Christ), with a poem of Rabanus Maurus overlaid. Vatican, Biblioteca Apostolica, Codex Reg. lat 124, f.4v
Charlemagne crowns Louis the Pious
Denarius of Louis
Louis the Pious doing penance at Attigny in 822
