Answer:
The Prussian chancellor Bismarck put forward a German candidate for the vacant Spanish throne and it provoked Napoleon III to declare war (1870-71). The disagreement between France and Prussia was a conflict that began when Bismarck tried to unify Prussia but the confederation of states specially the province of Alsace-Lorraine (which has a mixed French-German population) was claimed both by Prussia and France. This dispute, was won by the German Empire (formally called Prussia) in 1871, then became a primary motivating force behind both of the world wars. Ownership of the disputed province changed hands three times, between 1914-45. However, since France and Germany joined the European Community (now called the European Union) more than half a century ago, ethnic tensions in Alsace-Lorraine have not been allowed to spill over into a war.