<P> The German states proclaimed their union as the German Empire under the Prussian king Wilhelm I , finally uniting Germany as a nation - state . The Treaty of Frankfurt of 10 May 1871 gave Germany most of Alsace and some parts of Lorraine , which became the Imperial territory of Alsace - Lorraine ( Reichsland Elsaß - Lothringen ) . The German conquest of France and the unification of Germany upset the European balance of power that had existed since the Congress of Vienna in 1815 , and Otto von Bismarck maintained great authority in international affairs for two decades . French determination to regain Alsace - Lorraine and fear of another Franco - German war , along with British apprehension about the balance of power , became factors in the causes of World War I . </P>
<P> The German states proclaimed their union as the German Empire under the Prussian king Wilhelm I , finally uniting Germany as a nation - state . The Treaty of Frankfurt of 10 May 1871 gave Germany most of Alsace and some parts of Lorraine , which became the Imperial territory of Alsace - Lorraine ( Reichsland Elsaß - Lothringen ) . The German conquest of France and the unification of Germany upset the European balance of power that had existed since the Congress of Vienna in 1815 , and Otto von Bismarck maintained great authority in international affairs for two decades . French determination to regain Alsace - Lorraine and fear of another Franco - German war , along with British apprehension about the balance of power , became factors in the causes of World War I . </P>
when did germany take alsace-lorraine region from france in the franco-prussian war
when did germany take alsace-lorraine region from france in the franco-prussian war
10 May 1871
10 May 1871