The vanguard of the Emperor's and the Catholic League's army, led by Duke Charles IV of Lorraine and general Johann von Werth, caught up with Otto's rearguard at Willstätt, where he barely escaped capture.

Subsequently, Otto Louis took Freiburg im Breisgau and invested Rheinfelden while leaving a blockade corps at the remaining Habsburg stronghold Breisach.

Because Rheinfelden's garrison under Franz von Mercy tenaciously resisted until 19 August and Otto Louis only hesitantly set off to reinforce Horn, he arrived too late to participate at the Battle of Nördlingen and could only assist in collecting the hammered troops.

The bulk of the Imperial and Spanish armies advanced northwards upon Franconia, where Duke Bernhard of Saxe-Weimar, commander of the German Protestant forces, had withdrawn.

At the same time, Duke Charles IV of Lorraine, now appointed commander of the German Catholic League, and his cavalry general Johann von Werth invaded the duchy of Württemberg, a wealthy country where their troops could recover from the battle.

[6] On 27[1] or 28 September,[2] Wreth made contact with the enemy's rearguard at the village of Willstätt, between Offenburg and the Rhine river, while the bulk of the Swedish army was in Kehl in preparation for the crossing.

Under the terms of the Treaty of Paris, the Swedish handed over their fortresses and cities in Alsace with exception of Benfeld to France, in order to prevent the Imperials from taking control of the region.

[2] The Elector of Saxony opened talks with Ferdinand II, but the Landgrave of Hesse-Kassel and the Duke of Lüneburg still fielded troops against the Emperor and were in the surroundings of Frankfurt am Main.