スパルタクス団
At the end of 1914, Liebknecht, together with Rosa Luxemburg, Leo Jogiches, Hugo Eberlein, Paul Levi, Ernest Meyer, Franz Mehring and Clara Zetkin, formed the so-called Spartacus League ("Spartakusbund"). The Spartacus League publicized its views in a newspaper titled "Spartakusbriefe" ("Spartacus Letters") which was soon declared illegal. Liebknecht was arrested and sent to the eastern front during World War I despite his immunity as a member of parliament. Refusing to fight, he served burying the dead and due to his rapidly deteriorating health was allowed to return to Germany in October 1915.