are defined in the Bulls of approval and protection issued by Pope Adrian IV, 23 April 1155, and by Pope Innocent IV, 9 August 1245. The powerful Polish ruler Bolesław I was succeeded by his son Mieszko II Lambert, who had but a short reign. After his death a revolt against Christianity and the reigning family broke out, the new Church organization of Poland disappeared from view, and the names of the Bishops of Wrocław for the next half century are unknown. Casimir I, the son of Mieszko, and his mother were driven out of the country, but through German aid they returned and the affairs of the Church were brought into better order. A Bishop of Wrocław from probably 1051 to 1062 was Hieronymus, said by later tradition to have been a Roman nobleman. He was followed by John (1062–72), who was succeeded by Piotr I (1071–1111). During the episcopate of Piotr I, Count Piotr Włostowic entered upon the work of founding churches and monasteries which has preserved his name. Petrus was followed by: Żyrosław I (1112–20); Heymo (1120–26), who welcomed Otto of Bamberg to Wrocław in May 1124 when the saint was on his missionary journey to Pomerania; Robert I (1127–42), who was Bishop of Kraków; Robert II (1142–46); and Janik (1146–49), who became Archbishop of Gniezno. With the episcopate of Bishop Walter (1149–69) the history of the diocese of Wrocław begins to grow clearer. Pope Adrian IV, at Walter's request in 1155, took the bishopric under his protection and confirmed to it the territorial possessions of which a list had been submitted to him. Among the rights which the Pope then confirmed was that of jurisdiction over the lands belonging to the castle of Otmuchów, which had been regarded as the patrimony of the diocese from its foundation. In 1163 the sons of the exiled Polish duke Władysław returned from the Empire and, through the intervention of Emperor Frederick Barbarossa, received as an independent duchy the part of Silesia which was included at that date in the see of Wrocław. Bishop Walter built a new, massively constructed cathedral, in which he was buried. Żyrosław II (1170–98) encouraged the founding of the Cistercian monastery of Lubusz by Duke Bolesław I the Tall. In 1180 Żyrosław took part in the national assembly at Łęczyca at which laws for the protection of the Church and its property were promulgated. Jarosław