Sacerdotal Sovereignty and Holy War: The Papal Struggle with Frederick II, 1239–50

During the period c. 1239 to 1250, under Popes Gregory IX and Innocent IV, the Roman papacy waged what has been called a “total war” against the imperial power of the Hohenstaufen ruler, Frederick II. Scholars sometimes label this effort a “political crusade,” and leave it at that. This paper will explore the ideas and mechanisms behind the papal struggle with empire, situating them within the wider framework of contemporary ideas about the “sacerdotal sovereignty” of the Roman papacy. It will also offer some revisionist arguments about the significance assigned to medieval conflicts between “popes and emperors” in the historical separation of “church and state,” supposedly contributing to the secularization of Western civilization.