(b. 1885, d. 1939?).
Russian Communist Born Karl Sobelsohn, he was an active Social Democrat in Germany and Poland in 1901, and became a Bolshevik follower of Lenin after meeting him and other Russian Communist leaders in 1904. He worked as a journalist for the German Social Democrats from 1907, until he went to Russia to become a member of the central committee of the Petrograd Soviet in 1917. He subsequently became responsible for the development of the German Communist Party and frequently travelled to Germany, where his propaganda helped fuel the revolution of 1918. In 1924 he was released from his duty as a follower of Trotsky. Expelled from the Soviet Communist Party in 1927, he was readmitted in 1929, when he became active as a journalist. He was imprisoned in 1936 and sentenced to ten years' imprisonment early in the following year, which he did not survive.