The main purpose of this thesis has been to analyze the overall reasons for the German Social Democratic Party’s, SPD, change in policy by the end of the first World War, where the party turned away from their revolutionary foundation and instead fought actively against the revolution to preserve the existing society. In the period from the party’s foundation in 1860’s to the abolition of the antisocialist laws in 1890, we have found two essential factors which eventually influenced the party’s change in policy. Firstly, there is a division in the party from its foundation. The party is torn between the ideas of Ferdinand Lassalle and those of orthodox Marxist conviction, August Bebel and Wilhelm Liebknecht. The consequence of this becomes, that the party executive, afraid that division will eventually lead to a split in the newly founded party, decides to compromise with the party’s theoretical conviction and instead focus on party unity. Secondly, the party founds its theoretical conviction on Engels’ Anti-Dühring, which becomes an important tool for agitation for the party. This work had theoretical shortcomings in regard to Marx’ own work, but were nonetheless incorporated into the party’s official theoretical foundation. The shortcomings can ex. be seen in the works of the party’s leading theoretician, Karl Kautsky, in regard to his theory about revolution. In the period from 1890 to 1900 three factors influenced the party’s development. Firstly, there is the Erfurt Program, which incorporated the before mentioned theoretical inconsistencies, and through a section containing immediate tactical goals for the party, laid the foundation for the later inconsistencies between theory and practice, that ultimately tore the party apart. Secondly, the handling of the reformist leader Georg von Vollmar, who were not excluded from the party because of his massive support in Bavaria, even though he went against the party’s theoretical foundation. Thirdly, there is the handling of Eduard Bernstein after his challenge to the party’s orthodox Marxist foundation, which he wanted to revise. The party’s treatment of these two shows, that it fails to keep a stringent theoretical line already at the first challenges. Instead the party executive’s reaction is to give the building of a mass party priority over a consistent theoretical line. The period from 1900 to the outbreak of the First World War is characterized by the ongoing struggle between reform and revolution. It is in this period, that the rightwing consolidates its power within the party, which the appointment of Friedrich Ebert to party chairman attests to. In this period, there are numerous examples that show the rightwings increasing dominance within the party. A couple these are, that the party’s rightwing in cooperation with the unions took control over the use of mass strikes as a weapon in the struggle against the existing state, and that they engaged in parliamentary cooperation with the bourgeois parties (the Progressives and the National Liberals) in the 1912 election to the Reichstag. The last period covers the war and the revolution, 1914-1919. In this period we clearly see two essential themes, the SPD’s decision to support the war and their actions during the revolution. Before the war the rightwing is completely in control of the party, which forces supporters of the orthodox Marxist foundation together with those who oppose the war, to leave the party along with the leftwing. This resulted in the foundation of the USPD and the revolutionary Spartacist League. During the revolution the SPD strived to achieve absolute power and to preserve the existing society. The SPD is able to obtain power through their alliance with the army, and also because of the indecisiveness of the UPSD and the Spartacists. All in all our analysis draws a picture of a party that never completely overcomes its internal differences. As soon as one challenge has been overcome, the next problem presents itself, never allowing the party to settle and develop a clear political profile. The problematic relationship between theory and practice given in the Erfurt Program contributes to this. The party finds itself in a constant drift towards the right, even in the Bebel years. With Eberts appointment to chairman the party completely abolishes its former revolutionary character and participates consistently in the parliamentary process. And seeing that power is available and ultimately that their goals are attainable without revolution, the SPD fights actively against this radical change of society.