The NSF was politically repressed during the German occupation of Norway and, in the wake of World War II, experienced a dramatic decline.

[2] At a conference in Trondheim, syndicalists repudiated agreements with employers and instead endorsed methods of direct action to win workers' demands.

[8] The Norwegian syndicalists quickly developed close links with the Central Organisation of Swedish Workers (SAC), a relatively powerful anarcho-syndicalist union that counted 32,000 members by the end of the 1910s.

[1] After the conclusion of World War I, in February 1919, delegates from the NSF, SAC and the Danish Fagsoppositionens Sammenslutning (FS) met at a conference in Copenhagen to consolidate their international ties.

[17] Finally, in December 1922, the NSF was represented by Gus Smith at the constitutional convention of the International Workers' Association (IWA), which brought together more than 2 million members of anarcho-syndicalist trade unions from throughout Europe and Latin America.

[21] After World War II ended, although European anarcho-syndicalists had the possibility of returning to illegal activity, the movement entered a sustained decline.

[20] During the 1950s, Alarm resumed publication under the name Solidaritet, which remained in print until 1960; some short-lived anarcho-syndicalist groups were also established, including the Syndicalist Youth Alliance (Norwegian: Syndikalistiske Ungdomsforbund).