was a Saxon by birth, Otto appeared at the coronation in Frankish dress in an attempt to demonstrate his sovereignty over the Duchy of Lotharingia and his role as true successor to Charlemagne, whose last heirs in East Francia had died out in 911. According to Widukind of Corvey, Otto had the four other dukes of the kingdom (from the duchies of Franconia, Swabia, Bavaria and Lorraine) act as his personal attendants at the coronation banquet: Arnulf I of Bavaria as marshal (or stablemaster), Herman I, Duke of Swabia as cupbearer, Eberhard of Franconia as steward (or seneschal) and Gilbert of Lorraine as Chamberlain. By performing this traditional service, the dukes signaled cooperation with the new king, and clearly showed their submission to his reign. Despite his peaceful transition, the royal family was not harmonious during his early reign. Otto's younger brother Henry also claimed the throne, contrary to his father's wishes. According to her biography, , their mother had favored Henry as king: in contrast to Otto, Henry had been "born in the purple" during his father's reign and shared his name. Otto also faced internal opposition from various local aristocrats. In 936, Otto appointed Hermann Billung as Margrave, granting him authority over a march north of the Elbe River between the Limes Saxoniae and Peene Rivers. As military governor, Hermann extracted tribute from the Polabian Slavs inhabiting the area and often fought against the Western Slavic tribes of the Lutici, Obotrites, and Wagri. Hermann's appointment angered his brother, Count Wichmann the Elder. As the elder and wealthier of the two, Wichmann believed his claim to the office was superior to his brother's. Additionally, Wichmann was related by marriage to the dowager queen Matilda. In 937, Otto further offended the nobility through his appointment of Gero to succeed his older brother Siegfried as Count and Margrave of a vast border region around Merseburg that abutted the Wends on the lower Saale. His decision frustrated Thankmar, Otto's half-brother and Siegfried's cousin, who felt that he held a greater right to the appointment. Rebellion of the dukes Arnulf, Duke of Bavaria, died in 937 and was succeeded by his son Eberhard. The new duke quickly came into conflict with Otto, as Eberhard opposed the king's sovereignty over Bavaria under the peace treaty between King Henry and Arnulf. Refusing to recognize Otto's supremacy, Eberhard rebelled against the king. In two campaigns in