 In this struggle, the Elector was at first neutral, and for a long time he would not listen to the overtures of King Gustavus Adolphus of Sweden.Not until the Imperial General Johann Tserclaes of Tilly advanced into Saxony did the Elector join the forces of the Swedish Empire.However, after the 1634 Battle of Nördlingen, the Elector concluded the Peace of Prague with Emperor Ferdinand II in 1635.