With matters in southern Germany settled, Otto II turned his attention to defeating and capturing Henry II. After a failed first invasion into Bohemia, Otto II marched to Bohemia a second time in August 977. While in Bohemia, a revolt broke out in Bavaria. Henry I, Bishop of Augsburg, and the newly appointed Carinthian Duke Henry III joined Henry II in rebellion, forcing Otto II to return from Bohemia. The Emperor, aided by the Duke of Swabia and Bavaria, met the rebels at Passau and, after a long siege, forced them into submission. Otto II then brought the rebels before the Imperial Diet in Quedlinburg on March 31, 978. Boleslaus II was treated with honors and swore loyalty to Otto II. Mieszko I of Poland recognized Otto's royal authority to the throne. Otto II imprisoned Henry II under the custody of the Bishop of Utrecht where he would remain until Otto II's death in 983.