Hugo (Ugolino) of Segni, who as pope took the name Gregory, was born around 1170. While a cardinal (1198-1226), Hugo preached the Fifth Crusade in northern Italy as a joint papal-imperial legate (1217-1221) and witnessed the deleterious effects of the emperor Frederick II’s repeatedly delayed departure upon the enterprise.
Elected pope on 19 March 1227, Gregory invoked the excommunication previously accepted by Frederick as the penalty he would have to pay if he failed to fulfill his crusading vow on schedule (September 1227). Although Frederick’s crusade gained Christians access to Jerusalem through a ten-year truce with the Ayyûbid sultan al-Kāmil (February 1229), his excommunicate status and his political claims as husband of Isabella II, heiress to the kingdom of Jerusalem, caused lasting and debilitating divisions among the leaders ofOutremer. The emperor returned to rout the papal army that Gregory IX had sent to invade Sicily, leading to a temporary settlement of the papal-imperial conflict at the Treaty of San Germano (1230).
Although Gregory initially condemned Frederick’s treaty with al-Kāmil, it enabled him to pursue plans for crusades in other areas. After the legate Romanus successfully concluded the Albigensian Crusade at the Peace of Paris (1229), Gregory drew the mendicant orders, whom he had fostered from their very origins, into the earliest papal antiheretical inquisitions, as well as into crusade recruitment, mission work, and negotiations concerning reunion with the Greek church. Seeking to protect recent converts in the Baltic region from oppression by the Order of the Sword Brethren and other crusaders, Gregory used the Dominican Order to channel aid, in addition to papal and imperial privileges, to the Teutonic Order. In 1234 he began planning a crusade in expectation of the expiration of Frederick’s treaty in 1239, although a general passage to the Holy Land never materialized, as crusaders were diverted to other projects. Delayed by the papal-imperial struggle, yet hoping to protect Frederick II’s gains in the Holy Land, some crusaders led by Thibaud IV of Champagne and Richard of Cornwall reached Outremer in 1239 and 1240.
Gregory’s pontificate saw the first full application of crusading indulgences, privileges, and taxes to the struggle against the emperor, as well as the increasingly forceful commutation of crusaders’ vows from expeditions to Outremer to other enterprises that were portrayed as more urgent or equally essential for the preservation of the Holy Land. These measures and the diversion of the clerical income tax normally reserved for the crusade to the papal-imperial conflict foreshadowed the full development of political crusades against papal enemies by Gregory’s successor, Innocent IV. For after Frederick II sought greater influence in areas technically subject to the papacy, including Lombardy and Sardinia, Gregory excommunicated him in 1239, ordered a crusade to be preached against him in Lombardy and Germany, and convoked a general council meant to depose the emperor to be held in Rome in 1241. However, this project was ended by a blockade imposed on Rome by the emperor, during which Gregory died (22 August 1241).