French–German enmity ( ) was the idea of unavoidably hostile relations and mutual revanchism between Germans and French people that arose in the 16th century and became popular with the Franco–Prussian War of 1870–1871. It was an important factor in the unification of Germany and World War I, and was finally overcome after World War II, when under the influence of the Cold War cordial French–German relations became the key to European integration.