The formal unification of Germany into a politically and administratively integrated nation-state occurred on January 18, 1871, in the Hall of Mirrors at the Palace of Versailles. This event followed the Prussian victory in the Franco-Prussian War. Otto von Bismarck, the Minister President of Prussia, was the primary architect of unification, using a policy of 'Blood and Iron' to consolidate the various independent German states under Prussian leadership. King Wilhelm I of Prussia was proclaimed German Emperor (Kaiser). This created a new, powerful empire in the heart of Europe, fundamentally upsetting the 'Balance of Power' established by the Congress of Vienna and setting the stage for the industrial and military rivalries that would eventually lead to World War I.