 Against the advice of his brother, William swore an oath of office on the Prussian constitution and promised to preserve it "solid and inviolable".William appointed a liberal, Karl Anton von Hohenzollern-Sigmaringen, as Minister President and thus initiated what became known as the "New Era" in Prussia, although there were conflicts between William and the liberal majority in the Landtag on matters of reforming the armed forces.On 2 January 1861, Frederick William IV died and William ascended the throne as William I of Prussia.