Called by the Pope, Fought Across a Continent

The crusading movement began when Pope Urban II called for an armed expedition to recover Jerusalem and aid the Byzantine Empire against Turkish advances in a sermon preached at the Council of Clermont in 1095, an appeal that drew a much larger and more socially varied response than the pope had likely anticipated and resulted in the First Crusade's capture of Jerusalem in 1099. Central to the crusading institution as it developed was the indulgence, a remission of the temporal punishment due for sin granted by the church to those who undertook the campaign with proper contrition, which gave crusading a specific and unusual theological status among medieval Christian penitential practices, an act of arms treated as spiritually equivalent to pilgrimage.

Historians conventionally number a sequence of major crusades to the eastern Mediterranean running from the First in 1096 to the Ninth in the late thirteenth century, but the papacy also authorized crusades against targets much closer to home and considerably more diverse than the recovery of Jerusalem, including the Albigensian Crusade against the Cathars in southern France, the Baltic and Northern Crusades against pagan peoples, and crusades called against Christian political rivals of the papacy itself.