Passage: Thus, the entire SPD faction in the Reichstag voted in favour of the war bonds on 4 August 1914. It was with those decisions by the party and the unions that the full mobilisation of the German Army became possible. Haase explained the decision against his will with the words: "We will not let the fatherland alone in the hour of need!" The Emperor welcomed the so-called "truce" (Burgfrieden), declaring: "Ich kenne keine Parteien mehr, ich kenne nur noch Deutsche!" ("I no longer see parties, I see only Germans!").Even Karl Liebknecht, who became one of the most outspoken opponents of the war, initially followed the line of the party that his father, Wilhelm Liebknecht, had cofounded: he abstained from voting and did not defy his own political colleagues. However, a few days later he joined the Gruppe Internationale (Group International) that Rosa Luxemburg had founded on 5 August 1914 with Franz Mehring, Wilhelm Pieck, and four others from the left wing of the party, which adhered to the prewar resolutions of the SPD. From that group emerged the Spartacus League (Spartakusbund) on 1 January 1916.

Question: When did the Spartacus League emerge?
1 January 1916