During the 1866 Austro-Prussian War, Saxony sided with Austria, and the Saxon army was generally seen as the only ally to bring substantial aid to the Austrian cause, having abandoned the defense of Saxony itself to join up with the Austrian army in Bohemia.
Wilhelm I's grandson Kaiser Wilhelm II abdicated in 1918 as a result of Germany's defeat in World War I. King Frederick Augustus III of Saxony followed him into abdication and the erstwhile Kingdom of Saxony became the Free State of Saxony within the newly formed Weimar Republic.