GREGORY IV, POPE. — A Roman nobleman, priest of the title of St Mark, Gregory IV was elected pope without the intervention of the Emperor Louis the Pious, but was consecrated only after the arrival of an imperial legate who examined the election in accordance with the Constitution of 824; he reigned from 827 to 844. During the revolts of the sons of Louis the Pious against their father, Gregory IV unfortunately supported Lothair, the eldest son. Before crossing the Alps, he sent a letter to Agobard, archbishop of Lyons, prescribing prayers and fasts to invoke divine blessing upon the enterprise he was contemplating. In a formal invitation to the bishops to meet him, Gregory protested his peaceful intentions, namely to restore harmony between father and sons. While Agobard supported the Pope, condemning the attempts to divide the Empire made in 817, the imperialist bishops protested in a strongly worded collective letter against Gregory’s conduct in this matter. The Pope’s polemical reply did not enhance his authority, already compromised by his inglorious adventure. Pascasius Radbertus and Wala, who hastened to the Pope, vainly sought to suggest arguments to justify his action.
On his return from the ‘field of falsehood’, he found a new danger in Italy: the Arabs of North Africa, who had landed in Sicily in 827 and taken Palermo in 831. The Moors of Spain also ventured so far as to land on the Tyrrhenian coasts of Italy. To defend the mouth of the Tiber, Gregory IV had the fortifications of Ostia rebuilt (840–841), which he named Gregoripolis after himself. Moreover, Gregory IV proved himself in Rome a diligent restorer of both religious and civil buildings.
In 831–32 Gregory IV confirmed Ansgar, the ‘Apostle of the North’, as archbishop of Hamburg and appointed him papal legate to the Danes, Swedes and northern Slavs. In the case of Ebbo, archbishop of Rheims, Gregory IV was in no hurry to ratify the deposition sentence pronounced at Thionville in 835. Gregory IV died in January 844 after a seventeen-year pontificate.