Finally when the Investiture Controversy broke out and King Henry was excommunicated by Pope Gregory VII in February 1076, Duke Rudolf met with Berthold, Welf and several other princes in Trebur in order to decide on a course of action and to arrange a new election. Henry, observing the proceedings from his camp in Oppenheim on the other side of the Rhine, had to face a massive loss of support among the German nobles and realized that he had to achieve the lifting of his ban. Pope Gregory agreed to meet with the princes at Augsburg in February 1077.