Originally founded in protest against the SPD’s approval of the war and on the initiative of Rosa Luxemburg and labour movement historian Franz Mehring under the name of «Gruppe Internationale», the name «Spartacus Group” – derived from the «Spartacus Letters» published by the «Gruppe Internationale» from 1916 onward – soon replaced the original name. Members of the Spartacus Group were systematically persecuted for illegal anti-war propaganda activities, and their leaders, Rosa Luxemburg and Karl Liebknecht, imprisoned.
The Spartacus Group, which by 1917 had sought organisational refuge within the USPD, which, however, did not provide much help, and was considered to be teeming with police informers prior to the revolution. The Revolutionary Stewards may have helped distribute the leaflets of the Spartacus Group (which was intellectually superior to them), but apart from that they kept their distance.
At the beginning of the revolution in 1918 the Berlin Spartacus Group had 50 supporters, the USPD had 200,000. On 11 November 1918, the Spartacus Group was renamed the «Spartacus League», now an independent organisation. Alongside the party «Internationale Kommunisten Deutschlands», the league became the organisational and political nucleus of the Communist Party of Germany (KPD) founded on New Years’ Eve of 1918, as the Spartacus League’s leadership assumed the KPD’s overall leadership.