The Social Democratic Party of Germany (SPD - Sozialdemokratische Partei Deutschlands) is among the oldest political parties in Germany. Rooted in the worker's movement, it is left-of-center and subscribes to social democracy.
The party was founded in the late 19th century. After World War I, the Social Democratic Party and the Communist Party of Germany became bitter rivals. The leader of the Prussian government in Berlin, socialist Otto Braun was ousted by military coup on July 20, 1932 and the party was banned by the Nazis in 1933 and was recreated after World War II. In the Russian sector which later became East Germany, the Social Democratic Party and the Communist Party of Germany were forced to merge to form the Socialist Unity Party of Germany before regaining its status as a separate party after the fall of East Germany in 1991.
See Germany/Politics, and the party's own website, http://www.spd.de/