三帝同盟
Bismarck's main mistake was giving in to the Army and to intense public demand in Germany for acquisition of the border provinces of Alsace and Lorraine, thereby turning France into a permanent, deeply-committed enemy ("see" French–German enmity). Theodore Zeldin says, "Revenge and the recovery of Alsace-Lorraine became a principal object of French policy for the next forty years. That Germany was France's enemy became the basic fact of international relations." Bismarck's solution was to make France a pariah nation, encouraging royalty to ridicule its new republican status, and building complex alliances with the other major powers – Austria, Russia, and Britain – to keep France isolated diplomatically. A key element was the League of the Three Emperors, in which Bismarck brought together rulers in Berlin, Vienna and St. Petersburg to guarantee each other's security, while blocking out France; it lasted from 1881 to 1887.