Spartakus League The most important radical left group in the SPD, so called from its Politische Briefe (“Political Letters”), signed “Spartakus,” illegally distributed from 1916. These decisively rejected the Burgfrieden policy adopted by the majority of the Social Democratic Party. Leading figures in the Spartakus Group (later League) were Karl Liebknecht and Rosa Luxemburg, Franz Mehring, Clara Zetkin, Julian Marschlewski, and Käte and Hermann Duncker. The group’s support came predominantly from the existing intellectual …