150 years ago, the German Empire was proclaimed in the Hall of Mirrors of the Palace of Versailles: a revenge on the defeat of Jena in 1806. From the battle of Sedan in September 1870, followed by the surrender of France to Prussia, to January 18, 1871, the date on which King William I of Prussia was proclaimed emperor, the unification of Germany was largely built thanks to Otto von Bismarck. While in France the Second Empire had collapsed, the chancellor, through his power of persuasion, succeeded in obtaining the consent of the German princes.