Foster refutes common explanations blaming immigrants or working class prosperity for American labour's backwardness, identifying dual unionism—radicals abandoning mainstream unions to form separate organizations—as the true cause of the movement's weakness. Foster argues that this policy drained the vital "militant minority" from established unions, leaving them leaderless and stagnant under reactionary control while the dual unions themselves consistently failed and wasted immense revolutionary energy. The catastrophic results included destroyed unions like the Western Federation of Miners and the IWW's collapse, but by 1922, militants had abandoned dual unionism in favour of working within existing unions to revitalize the labour movement.