Liebknecht, Karl (kärl lēpˈkənĕkht) [key], 1871–1919, German socialist, leader of the Spartacus party; son of Wilhelm Liebknecht. His antimilitaristic writings caused his conviction (1907) for high treason. Released from prison, Liebknecht entered the Prussian lower house in 1908 and the Reichstag in 1912. As a member of the extreme left wing of the Social Democratic party, he refused to support the government during World War I. In 1915 he and Rosa Luxemburg formed the Internationale, a revolutionary, antiwar socialist group. This group later became the Spartacus party. Imprisoned again for his antiwar activities, Liebknecht was released just before the proclamation of the German republic in Nov., 1918. With Rosa Luxemburg he opposed the moderate government formed by the Social Democrats and advocated its violent overthrow. Shortly afterward, the Spartacists were reconstituted as the German Communist party. In Jan., 1919, Liebknecht led an uprising against the government. After its failure he was arrested and killed while being taken to prison.
See K. W. Meyer, Karl Liebknecht (1957).