 When the Kingdom of Serbs, Croats and Slovenes was created after World War I, the different social democratic parties that had existed in Austria-Hungary, Serbia and Montenegro called for a unification of their parties.In 1919, a congress was held in Belgrade where Bolshevik influence was introduced by soldiers who during the war had been captured by Russian forces and had experienced the October Revolution.It resulted in the creation of the Communist Party of Yugoslavia.