During his relatively short tenure as pope, Gregory IX (ca. 1145-1241) named many new cardinals, established the medieval Inquisition, promulgated a code of canon law, and twice excommunicated Roman Emperor Frederick II.

Ugo (Ugolino) di Segni was born around 1145 at Anagni in the Campagna region of Italy. His father was Count of Segni and his uncle would become Pope Innocent III. Young Ugo was provided a strong education, attending the universities of Bologna and Paris, where he studied theology and law. He was a deeply religious man and pursued his spiritual calling with vigor and enthusiasm. Little is known about his early years as a priest.

In 1198, with the ascension of his uncle to the papacy, Ugo di Segni was appointed papal chaplain, then archpriest of St. Peter's, and finally cardinal-deacon of St. Eustachio. In May 1206, Pope Innocent III promoted him to cardinal-bishop of Ostia and Velletri.

In...