 They were willing to surrender, but they demanded the deposition of Antipope Clement III.Henry was inclined to accept their offer, but his bishops dissuaded him, fearing they would also be dismissed after the Antipope's fall.To prevent further negotiations between the Emperor and his opponents, Pope Urban II mediated a marriage alliance between Welf I of Bavaria's 18-year-old son, Welf the Fat, and the 43-year-old Matilda of Tuscany in the autumn of 1089.