ABSTRACT
Gregory IX (1227-41), born at Agnani in ca. 1170, was probably fifty-seven when he became pope and enjoyed a long pontificate of fourteen years. Like his predecessors Innocent III (1198-1216) and Honorius III (1216-27), throughout his time as pope he was deeply involved in complex diplomatic relations with the Holy Roman Emperor Frederick II (1220-50), against whom he finally took the decision to authorize a crusade in 1239, a move which would sour relations between the papal curia and Hohenstaufen emperors for decades.1 Yet, despite his preoccupation with imperial politics, during his time in office Gregory also set a precedent in authorizing several new crusades against groups living in Christian Europe who were accused of heresy.2 His authorization of such crusades was influenced by the wishes of local political leaders and prelates who looked to the papacy for support and endorsement of such military campaigns against suspected heretics.
