Bauer, Otto (bouˈər) [key], 1882–1938, Austrian politician. His Die Nationalitätenfrage und die Sozialdemokratie (1907) advocated creating nation-states to solve the Austro-Hungarian nationalities problem. A prisoner of war in Russia during World War I, he led the left wing of the Social Democratic party when he returned, presenting them as a third force between the Communists and nationalists in the revolution of 1918. Named secretary of foreign affairs (1918) in the new Austrian republic, he signed a secret Anschluss agreement with Germany (1919) that was repudiated by the Allies. He resigned in 1919, and led the opposition to conservative governments. He was the guiding personality of the Social Democrats and the principle advocate of unification with Germany. His second theoretical work was Die Österreichische Revolution (1923). The failure of a socialist workers' revolt (1934) led to his exile abroad. He died in Paris.