The end of the Franco-Prussian war witnessed the detachment of Alsace and Lorraine from France and their incorporation into a united Germany ( 1871). This event set off a debate on the true nationality of the inhabitants, given that they had been part of the Holy Roman Empire, a German-based medieval construction dissolved only in 1806 but which had lost all practical significance at least since 1648. This debate exacerbated tensions between France and Germany; French political forces demanded a war of revenge, and the Germans smoldered over their alleged mistreatment at French hands over the centuries.
In France the debate gained intensity and changed character with the Dreyfus affair. In 1894 Captain Alfred Dreyfus, a Jew, was accused of selling military secrets to Germany. He was tried and condemned to Devil's Island. His family consistently believed in his innocence and worked to reopen the case. They enlisted the aid of Émile Zola, a famous novelist of the period. Although Dreyfus was eventually retried and found guilty once again, new evidence pointed to his innocence, and the ultimately successful struggle to free him raged unabated. The case split French society, dividing supporters of the Third Republic (established in 1870) from its detractors, church and state, left and right, army and civilian government. Up to that time the drive for a war of revenge against Germany animated the left, which appealed to the revolutionary values of 1789-1794 against the premier European conservative power; now the right took over the notion of an anti-German crusade, basing the idea on nationalism.
As the Dreyfus affair heated up, so did French patriotic furor and anti- Semitism, intimately linked to French nationalist ideology. The debate-- fueled by nationalist associations such as the Ligue de la Patrie Franaise