 From March to June 1620 George Frederick blocked the road from Breisach to Freiburg by order of the Protestant Union, operating from a fortified camp at Ihringen.The goal was to prevent the passage of mercenary troops of Bavaria and the Catholic League from the Alsace to their assembly points at Lauingen and Dillingen on the Danube.Nevertheless, after Emperor Ferdinand II gave assurances that certain troops had been recruited for himself and not for Bavarian/Catholic League army, George Frederick allowed the three regiments to pass and had to put up with being called naïve when these regiments joined the army of Duke Maximilian I of Bavaria.