Papal election, 1241

The papal election, following the death of Pope Gregory IX, from September 21 to October 25, 1241 elected Cardinal Goffredo da Castiglione as Pope Celestine IV. The election took place during the first of many protracted sede vacantes of the Middle Ages, and like many of them was characterized by disputes between popes and the Holy Roman Emperor. Specifically, the election took place during the war between Frederick II, Holy Roman Emperor against the Lombard League and the deceased pontiff, Pope Gregory IX, with Italy divided between pro-Papal and pro-Imperial factions known as the Guelphs and Ghibellines.

During the sede vacante, Frederick II surrounded Rome with his armies, blocking the arrival of some cardinal electors known to be hostile to his interests. Unable to reach a consensus, the cardinals were locked in a monastery called the Septasolium (corrupted in both medieval and modern narratives into Septizodium) by the Roman civic officials, eventually settling on one of their oldest and most feeble members. The conditions within the building were believed to have contributed to the death of one of the papabile and even to the death of Celestine IV soon after the election. Following Celestine IV's death, the war on the peninsula resumed and the cardinals dispersed for over a year and a half before coming together in Anagni to elect Pope Innocent IV.

The forced sequestration of the cardinals during the election was historically significant, and—along with other papal elections of the 13th century—contributed to the development of the papal conclave.

The papacy of Pope Gregory IX (1227–1241) and the kingship of Frederick II, Holy Roman Emperor took place at a time when centuries-old disputes between the popes and emperors were coming to a head. Frederick II had dedicated troops, but not his own leadership, to the failed Fifth Crusade, to the dismay of the church; following his marriage to Yolande of Jerusalem, he took up the Sixth Crusade but later abandoned it and returned to Italy, for a variety of political, economic, and military reasons. This served as a pretext for his excommunication by Gregory IX, and thinly veiled skirmishes between supporters of the pope and emperor (Guelphs and Ghibellines, respectively) throughout the Italian peninsula, particularly in Lombardy. Before his death, Gregory IX had called for a synod to denounce Frederick II, and the emperor had gone to great lengths to disrupt the gathering, including the imprisonment of captured prelates and cardinals.

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