The Iron Front was formed on 16 December 1931 in the Weimar Republic by the Social Democratic Party (SPD), along with the Allgemeiner Deutscher Gewerkschaftsbund (ADGB), the Reichsbanner Schwarz-Rot-Gold, and workers' sport clubs.[3] The Iron Front chiefly opposed the paramilitary organisations of the fascist National Socialist German Workers Party (NSDAP) and the Communist Party of Germany (KPD). Its initial purpose was to counter the right-wing Harzburg Front.