In 1866 the Austrians suffered defeat in the Austro-Prussian War and the Hessian grandduchy was in jeopardy of being awarded as the spoils of war to victorious Prussia, which annexed some of Austria's other allies (Hanover, Hesse-Cassel, Nassau), a fate from which Hesse-Darmstadt appears to have been spared only by a cession of territory and the close dynastic kinship between its ruler and the Emperor of Russia (Alexander II's consort, Empress Maria Alexandrovna, was the sister of Hesse's Grand Duke Louis III and of Prince Charles).