Independent Social Democratic Party of Germany

In August 1914 the SPD Reichstag members bowed to party discipline and all voted for war bonds, but opposition votes grew, beginning with Karl Liebknecht. In June 1915 Karl Kautsky, Hugo Haase and Eduard Bernstein published The Order of the Day, demanding a negotiated peace without annexations. The 18 deputies who voted against war bonds in December 1915 were expelled from the parliamentary group in March 1916 and formed the Social Democratic Working Group, and on 18 January 1917 Friedrich Ebert had them and the Spartacus League expelled from the party. The Working Group’s conference held at Gotha, the city of the 1875 Unification Congress, on 6–8 April 1917 founded the USPD. Haase and Georg Ledebour were elected chairmen, and the party brought together traditionalists such as Haase, revisionist opponents of the war such as Eisner and Bernstein, the theorist Kautsky and the revolutionaries of the Spartacus group.

Membership was about 120,000 a few months after the founding according to the English-language source, and about 100,000 in the founding year according to the German-language source, which adds that it peaked at almost 900,000 in 1920. The party played a major role in the mass strikes of April 1917 and January 1918. In the November Revolution of 1918 Haase, Wilhelm Dittmann and Emil Barth formed the Council of the People’s Deputies together with three Majority Social Democrats, and in Bavaria Kurt Eisner became minister-president. After the Christmas crisis, in which government troops attacked the People’s Navy Division, the three resigned from the council on 29 December 1918. On 1 January 1919 the Spartacus League left to found the Communist Party of Germany, and that month the dismissal of Berlin police chief Emil Eichhorn sparked the Spartacist uprising.

In the National Assembly election of January 1919 the party won only 7.6%, and no USPD member voted for the Weimar Constitution in the final vote. Haase died on 7 November 1919 of wounds from an assassination attempt on 8 October. The Leipzig congress of November–December 1919 adopted Arthur Crispien’s action programme calling for the bourgeois state to be “smashed” and replaced by political workers’ councils, and Crispien and Ernst Däumig were elected chairmen. In the Reichstag election of June 1920 the party rose to 17.6% of the vote and from 22 to 83 seats, becoming the second-strongest party after the Majority SPD.

The Halle congress of October 1920 accepted the Comintern’s 21 conditions by 236 votes to 156, and the party split. The left wing merged with the KPD in December 1920 to form the United Communist Party of Germany; the English-language source puts it at about 400,000 members, while the German-language source says up to about 550,000 joined the left USPD and that the United Communist Party had about 448,500 members in January 1921. The right wing under Ledebour and Crispien, with about 340,000 members and three-quarters of the Reichstag deputies, kept the name. After the assassination of Walther Rathenau in June 1922 the right USPD reunited with the Majority SPD at a joint congress in Nuremberg on 24 September. A minority under Ledebour and Theodor Liebknecht refused, survived as a splinter party and joined the Socialist Workers’ Party of Germany in 1931.