Pope Nicholas I (858–67), one of the few great popes between Gregory I and Gregory VII. He forced Lothair II of Lorraine to take back his first wife, Theutberga, whom he had divorced, and deposed the archbishops of Trier and Cologne for endorsing the divorce; affirmed the right of suffragan bishops to appeal directly to Rome over their metropolitan in a case involving the powerful Hincmar, archbishop of Reims; encouraged Sts. Cyril and Methodius in their missionary work among the Slavs (See 863–85); and, in the bitter controversy over the patriarchate of Constantinople, supported Ignatius and excommunicated Photius (863). Nicholas first propounded the theory that no bishop may be elected or deposed without papal approval.
Decline of the papacy, after the pontificate of Nicholas and the death of Louis II. As the popes had no powerful protectors outside Italy until 961, they fell increasingly under the dominance of the Roman and Italian aristocracy. The lapse of the imperial power left room for the insinuation of a new doctrine of papal autonomy, well formulated in the Forged Decretals. Outside Italy the relaxation of papal control and the decline of papal prestige, accompanied by the rise of dominant local feudal lords, accentuated the power of the bishops and made the unity of the Western Church a mere shadow until the papacy, having learned to cope with feudalism in the second half of the 11th century, once again made its influence felt in the Church.
Emperor Charles the Bald continued to support the papacy against the invader and came to Rome (875) to be crowned, having forced Charles the Fat to retreat and having induced his brother Carloman to sign a truce and withdraw. He was then elected king of Italy by the local magnates.
