History of Germany during World War I
In November 1918, with internal revolution, a stalemated war, Bulgaria and the Ottoman Empire suing for peace, Austria-Hungary falling apart from multiple ethnic tensions, and pressure from the German high command, the Kaiser and all German ruling princes abdicated. On 9 November 1918, the Social Democrat Philipp Scheidemann proclaimed a Republic, in cooperation with the business and middle classes, not the revolting workers. The new government led by the German Social Democrats called for and received an armistice on 11 November 1918; in practice it was a surrender, and the Allies kept up the food blockade to guarantee an upper hand. The war was over; the history books closed on the German Empire. It was succeeded by the democratic, yet flawed, Weimar Republic.
Constitution of the German Empire
The empire was officially defined as a federation of the member states under the presidency of Prussia. The King of Prussia was automatically the bearer of the "Bundespräsidium", since 1 January 1871 additionally with the title "German Emperor" ("Deutscher Kaiser"). Therefore, the imperial crown was tied to the "office" of the King of Prussia instead of a personal union between the Empire and Prussia. This meant that contrary to what Wilhelm II believed at the end of World War I, he could not abdicate merely as German Emperor while keeping the Prussian crown unless he agreed to renounce the entire constitution, which would have been, in effect, the "de jure" dissolution of the Empire.