Karl Liebknecht was already a leader of the SPD’s left wing before World War I. True to his consistently pacifist convictions, he rejected his party’s leadership’s Burgfrieden policy and voted against war credits. In 1916, he was excluded from the SPD’s parliamentary group. He founded the “International” group and left the SPD for the USPD in 1917. He was imprisoned for several years because of his opposition to the war and was not released until the November Revolution. Thereafter, as a leader of the Spartacists, he pushed for a councils-based dictatorship in Germany modelled after the Russian system. He helped found the KPD. Liebknecht played a major role in the so-called Spartacist Uprising in Berlin in January 1919. He was murdered by Freikorps troops shortly thereafter.

Wikipedia entry

Rosa Luxemburg is doubtlessly the most famous socialist among German speakers. The brilliant theoretician and rhetorical genius was a leader of the left wing of the workers’ movement. During the November Revolution, she pushed for a councils-based republic and was a leading figure of the Spartacists and the KPD. In January 1919, she was murdered by the Freikorps.

Wikipedia entry

Leo Jogiches was from Lithuania and championed a social revolution early on. He fled to Switzerland when the czar’s secret police started chasing him down. During World War I, he lived underground and during the November Revolution, he helped found the KPD. After Karl Liebknecht and Rosa Luxemburg were murdered, the reins of the young party were put in his hands. True to Luxembourg’s policy, he too took a stance against the primacy of the Russian Bolshevists within the Communist International. During the Märzkämpfe, the bloody clashes in Berlin in March 1919, Leo Jogiches was arrested and murdered from behind while in police custody.

Wikipedia entry

Ernst Thälmann joined the SPD in 1903. However, after the November Revolution, he turned to the USPD, only to leave it later on to join the KPD. He became famous during the “German October” of 1923 when leading the Hamburg Uprising, which was supposed to serve as a torch lighting a revolution in Germany. The attempt failed miserably. From 1925, he served as the KPD’s chairman and transformed it, step by step, into an organization dependent on Moscow. He stood for Reichspräsident in 1925 and his adversaries accused him of having made Hindenburg’s electoral win possible by participating in the second round. Ernst Thälmann fervently advocated the “social fascism” thesis, thereby deepening the division within the workers’ movement. He did not recognize the danger of the NSDAP until a late stage. In March 1933, he was arrested and in 1944 he was shot in the Buchenwald concentration camp per Hitler’s orders, after eleven years of imprisonment.

Wikipedia entry

Together with Rosa Luxemburg, Clara Zetkin was a female leader of the SPD’s left wing before World War I. She became famous for her work promoting the emancipation of women. After the KPD was founded, she joined it; however, she was mostly active within the party’s right wing because she refused to follow - without any criticism - the instructions of the Communist International and the Bolshevists. From 1920 to 1933, she served in the Reichstag, where she held a courage speech warning against national socialism in 1932 as the Mother of the House. In 1933, Zetkin went into exile in the Soviet Union and died there a short time later.

Wikipedia entry