Sweden is renowned for its peaceful industrial relations during the post-WWII years. But in the first three decades of the twentieth century Sweden was struck by extensive labour and employer militancy. The internationally established explanation for this transformation from peak to trough is the seizing of governmental power by the social democrats in the 1930s. Instead I claim that the development of, and the shifting balance of power between, the major working class ideologies - communism, syndicalism and social democracy - was an important factor in the decline of industrial strife.