Oncken, Hermann (hĕrˈmän ôngˈkən) [key], 1869–1946, German historian. He taught at the universities of Heidelberg, Munich, Chicago, and (1928–35) Berlin. He was forced to retire because of his opposition to the Nazi regime. Among his chief works are Napoleon III and the Rhine (1926, tr. 1928, repr. 1967) and a history (1933) of Germany from 1870 to World War I. His other writings include essays and excellent biographies of Ferdinand Lassalle (1904) and of Rudolf von Bennigsen (1910). Oncken also edited diplomatic documents dating from 1858 to 1871.