 The latent tensions between Sigismund, King of Germany and Frederick IV, Duke of Austria exploded in 1415 at the Council of Constance, when Frederick assisted one of the three then reigning popes, Antipope John XXIII, in escaping from the town.Sigismund took the opportunity to harm his opponent, ordering his neighbours to seize his lands in the name of the Empire.Bern willingly conquered the western part of the Aargau.