Meantime on land the Slavic barbarians, the Wends, the Czechs, and the Obotrites, rebelled against the German yoke and threatened the whole north-eastern border of the Empire. Behind them were the Poles and Russians. Farther south came the unruly Hungarian tribes which "dashed over Germany like the flying spray of a new wave of barbarism, and carried the terror of the battle-axes to the Apennines and the ocean."[389:1] These blows from all sides knocked out the foundations of the imperial structure, already weakened to the point of dissolution by internal decay, and it fell. As a result reliance for protection on a common defence and imperial organisation was abandoned. Feudalism replaced the Empire. The strong built fortress castles, the weak became their vassals. Local authorities--counts, dukes, lords, bishops, and abbots--saw new duties and new opportunities. They took a firmer hold, converted a delegated into an independent power, a personal into a territorial jurisdiction. Recognition of a distant, weak imperial or royal authority was only nominal and feeble at that. The grand dream of a mighty, universal Christian Empire was being rapidly lost in the decentralising forces, and in the increasing localisation of all powers. During this period of weakness and confusion, the mediæval Church, instead of standing forth as the source of strength and intelligence, instead of making further gains of a political and ecclesiastical character for the See of St. Peter, seemed to fall into "a death-sleep of moral and spiritual exhaustion."[389:2] The Papacy as a religious organisation almost disappears from view. The commanding spirits of Gregory the Great and of Nicholas the Great were utterly forgotten. The victories gained through the Pseudo-Isidorian Decretals were not followed up. A really great Pope at this time might easily have realised all the dreams of Innocent III., but none such wore the papal tiara.