In 1557, the Aš region was finally incorporated into the Lands of the Bohemian Crown by the Habsburg king Ferdinand I. Like the neighbouring Egerland, it remained Protestant until the Thirty Years' War, as the Counter Reformation did not stretch to the West Bohemian borderlands. In the 1648 Peace of Westphalia, the Protestant confession of the citizens was confirmed. In 1774, Empress Maria Theresa officially mediatised Aš as part of the Bohemian crown land within the Habsburg Monarchy, against the delaying resistance by the Zedtwitz noble family. Nevertheless, she granted its Protestant citizens freedom of religion, confirmed in the 1781 Patent of Toleration, issued by her son Emperor Joseph II.