which lay within of the diocese. Bishop Notger (972–1008) and his successors are thus referred to as princes within the Holy Roman Empire. This situation continued until the French Revolution, and throughout that period of nearly eight centuries the Prince-Bishopric of Liège succeeded in maintaining a level of autonomy, though it remained under the emperor. This virtual independence was owed largely to the ability of its bishops, who on several occasions played an important part in international politics, being strategically positioned between France and Germany. Throughout the Middle Ages, the prince-bishopric was further expanded with the lordship of Bouillon in 1096 (ceded to France in 1678), the acquisition of the county of Loon () in 1366 and the county of Horne in 1568. Notger, the founder of the principality, also rebuilt the cathedral of St Lambert, as well as the episcopal palace. He was also involved in other building activities in the city, which flourished under his rule (churches of St Paul, St. John the Evangelist, Sainte-Croix and St Denis). This bishop also strengthened the parochial organization of the city. He was one of the first church leaders to spread the observance of All Souls' Day, which he authorized for his diocese. Under Notger's administration, following up on the work of Heraclius, educational institutions in Liège flourished. With these two bishops (and Wazo) "The schools of Liège were, in fact, at that time one of the brightest literary foci of the period". In the 11th century the city was indeed known as the Athens of the North. "Liège for more than a century occupied among the nations a position in regard to science which it has never recovered". Subsequent bishops, Balderic of Looz (1008–18), Wolbodo (1018–21), Durandus (1021–25), Reginard (1025–38), Nitard (1038–42), the learned Wazo, and Theoduin (1048–75), valiantly sustained the heritage of Notger. The schools formed many brilliant scholars, and gave the Catholic Church popes Stephen IX and Nicholas II. The diocese also supplied the University of Paris with a number of important doctors — William of Saint-Thierry, Gerard of Liège and Godfrey of Fontaines. Alger of Liège (1055–1131) was an important intellectual of the period. He was first appointed deacon of church of St Bartholomew and finally retired at the monastery of Cluny. In the reign of Henry of Verdun (1075–91) a tribunal was instituted () to prevent war and enforce the Peace of God. Otbert (1091–1119) increased