A Bull of the Crusade (Spanish: Bula de la Cruzada) was a Papal bull that granted indulgences to those who took part in the crusades against Muslims, pagans or sometimes heretics (from the Catholic viewpoint). These indulgences were similar to those that, as far back as the 11th century, had been granted to the faithful of the Spanish Mark who took part in building churches and monasteries, or who gave alms to be devoted to this purpose.