Reichsacht
Under the terms of the Western Schism, Duke Frederick sided with Antipope John XXIII, whom he helped on his flight from the Council of Constance in March 1415. The Luxembourg king Sigismund had John arrested in Breisgau and placed Frederick under the Imperial ban. Thanks to the support of the local populace he managed to keep Tyrol, though he lost the western Aargau, the Freiamt and County of Baden estates, in the old homeland of the Habsburgs, to the Swiss.