However, Ernst von Mansfeld continued to occupy a portion of the Upper Palatinate and had successfully resisted efforts by Johann Tserclaes, Count of Tilly to dislodge him. Mansfeld crossed into the Rhenish Palatinate in early 1622, and on 21 April 1622, Frederick joined Mansfeld there. Frederick attempted to convince other Protestant princes to reconstitute the Protestant Union, but met with limited success. Frederick's cause was boosted by a 27 April 1622 victory over Tilly's forces at the Battle of Wiesloch, but this boost was short lived. Frederick's forces under the command of Georg Friedrich, Margrave of Baden-Durlach were defeated at the Battle of Wimpfen on 6 May 1622; and then forces under Christian the Younger of Brunswick were soundly defeated at the Battle of Höchst on 20 June 1622.