 Henry expelled his son's troops from Würzburg in August, but his authority was quickly waning.His son took advantage of Frederick of Büren's death to take control of Swabia.Leopold III, Margrave of Austria, and Bořivoj II, Duke of Bohemia, deserted the Emperor at Regensburg in late September, though Bořivoj soon repented his betrayal, and supported Henry's flight from Regensburg to Saxony.