The FS experienced a surge in growth during World War I as the social-democratic unions failed to keep up with the rising cost of living while the syndicalists secured reductions in working hours and wage increases.
The growth of syndicalism in Denmark was slower than in Norway and Sweden, as Danish trade union leaders had been able to establish collective bargaining rights much earlier than in the other Scandinavian countries.
[1] But following a wave of lockouts, when the social-democratic leadership of Danish trade unions agreed to a compromise deal with business owners, disillusionment among the rank-and-file began to increase.
[4] In 1910, he established the Trade Union Opposition Federation (Danish: Fagoppositionens Sammenslutning; FS), which became the country's main syndicalist organisation during the 1910s.
[9] Over the subsequent years, the FS increased its trade union presence, gaining the adhesion of blacksmiths, mechanics, dockworkers and construction workers in the Danish capital.
Social democrats infiltrated syndicalist meetings to disrupt their proceedings and report on their activities to the party leadership, with one interrupting a speech by Christensen on syndicalism in France to defend the social-democratic unions in Denmark and Germany.
[12] The FS was closely connected to the Central Organisation of Swedish Workers (SAC), a relatively powerful syndicalist union with 32,000 members in several industries.
[14] In 1915, Albert Jensen moved to Denmark, where he became a leading writer for Solidaritet, penning a number of articles that were critical of the Norwegian Syndicalist Federation (NSF).
[9] The material conditions brought on by the war caused a substantial growth in the syndicalist movement, as the Danish working classes were radicalised by the perceived failure of the social democrats.
[8] In March 1920, King Christian X dismissed the social liberal government of Carl Theodor Zahle, causing the Easter Crisis.
[26] Within a year, the Danish syndicalist movement had declined from a height of mass strike actions and trade union organising to effectively disappearing.
[32] After the founding congress of the RILU in July 1921, revolutionary syndicalist delegates, including those from Denmark, decided to instead establish their own trade union international.
[33] In December 1922, a delegate for the Union for Syndicalist Propaganda (Danish: Syndikalistik Propagandaforbund; SPF) participated in the founding congress of the International Workers' Association (IWA).