Gregory IX, 1143?–1241, pope (1227–41), an Italian named Ugolino di Segni, b. Anagni; successor of Honorius III. As cardinal under his uncle, Innocent III, he became, at St. Francis' request, the first cardinal protector of the Franciscans. About 84 when he was elected, he was a vigorous pope despite his age. He immediately commanded Holy Roman Emperor Frederick II Frederick II, 1194–1250, Holy Roman emperor (1220–50) and German king (1212–20), king of Sicily (1197–1250), and king of Jerusalem (1229–50), son of Holy Roman Emperor Henry VI and of Constance , heiress of Sicily.
..... Click the link for more information. to keep his vow to go on crusade and excommunicated (1227) him when he delayed. The imperialists in Rome forced (1228) the pope into exile until 1230, when emperor and pope were reconciled. Five or six years later the struggle broke out again, this time over Italian liberties. Gregory again excommunicated (1239) Frederick and ordered his dethronement. Frederick prevented circulation of the bulls in Germany and blocked a general council summoned by Gregory. Gregory died at 98 when Frederick was about to attack the city. He was succeeded by Celestine IV. Gregory ordered the first complete and authoritative collection of papal decretals, the Corpus Iuris Canonici, which remained a fundamental source of canon law until the promulagtion of the Codex Iuris Canonici in 1917. Gregory IX organized (1233) the Inquisition and gave special responsibility for it to the Dominicans.

Gregory IX

orig. Ugo di Segni

(born before 1170—died Aug. 22, 1241, Rome) Pope (1227–41) who founded the papal Inquisition. In 1227 he excommunicated Frederick II when the emperor delayed in keeping his pledge to lead a Crusade. Gregory ordered an attack on the kingdom of Sicily in the emperor's absence, but his forces were defeated. In 1234 he published the Decretals, a code of canon law that remained fundamental to Catholicism until World War I. Attacking heresy in southern France and northern Italy, he strengthened the Inquisition. Frederick's invasion of Sardinia, a papal fief, led Gregory to renew his excommunication (1239); he sought support in northern Italy but died before the struggle was resolved.