ALEXANDER IV. (Rinaldo), pope from 1254 to 1261, was, like Innocent III and Gregory IX, a member of the family of the counts of Segni. His uncle Gregory IX made him cardinal deacon in 1227 and cardinal bishop of Ostia in 1231. On the death of Innocent IV he was elected pope at Naples on the 12th of December 1254. He is described as a stout man, kindly, cheerful, but of no great brilliancy. He succeeded Innocent IV as guardian of Conradin, the last of the Hohenstaufen, promising him his benevolent protection; but in less than a fortnight he conspired against him and bitterly opposed Conradin's uncle Manfred. Alexander fulminated with excommunication and interdict against the party of Manfred, but in vain; nor could he enlist the kings of England and Norway in a crusade against the Hohenstaufen. Rome itself became too Ghibelline for the pope, who withdrew to Viterbo, where he died on the 25th of May 1261. His pontificate was signalized by efforts to unite the Greek and Latin churches, by the establishment of the Inquisition in France, by favours shown to the mendicant orders, and by an attempt to organize a crusade against the Tatars.
Initial text from 1911 encyclopedia -- Please update as needed