Conrad's reign was a continuous and generally unsuccessful struggle to uphold the power of the king against the growing power of the local dukes. His military campaigns against Charles the Simple to regain Lotharingia and the Imperial city of Aachen were failures. Archbishop Ratbod of Trier even became West Frankish chancellor in 913. Conrad's realm was also exposed to the continuous raids of the Magyars since the disastrous defeat of the Bavarian forces at the 907 Battle of Pressburg, leading to a considerable decline in his authority. His attempt to mobilize the East Frankish episcopate led by Archbishop Unni of Bremen to his cause at the 916 synod of Hohenaltheim was not enough to compensate other failures. After several clashes, Conrad at least was able to come to terms with duke Henry of Saxony. The restless Swabian dukes Erchanger (executed in 917) and Burchard II were a continuous threat, as was Arnulf, Duke of Bavaria.