Karl Paul August Friedrich Liebknecht was a German socialist, originally in the Social Democratic Party of Germany and later a co-founder with Rosa Luxemburg of the Spartacist League and the Communist Party of Germany which split away from the SPD. He is best known for his opposition to World War I in the Reichstag and his role in the Spartacist uprising of 1919. The uprising was crushed by the SPD government and the Freikorps. Liebknecht and Luxemburg were murdered.
After their deaths, Liebknecht and Luxemburg became martyrs for socialists. According to the Federal Office for the Protection of the Constitution, commemoration of Liebknecht and Luxemburg continues to play an important role among the German left, including Die Linke.