Through an analysis of the internal politics of the unions, the dissertation shows that there were factions advocating the two types of unionism in Tekkororen and Kokuro in the earlier postwar period, but that the leadership of the unions came to be dominated by the factions that advocated cooperative economic unionism and militant political unionism, respectively. The dissertation links the development of these polarized policy orientations to interactions among the unions, management, and the state. The management of the steel firms strongly influenced the development of the internal politics of Tekkororen in such a way that the pro-management faction dominated the union leadership. In the case of Kokuro, the militant policy orientation prevailed because of confrontations between union and the state due to frequent state intervention into the union-management relations of the Japan Naitonal Railways.
Based on the analysis, the dissertation argues that the interests of union members do not directly reflect social values or socio-economic structures, but are defined through politics played within unions as well as among unions, management, and the state. It also casts doubt on the implicit assumption of previous theories of union politics that the internal political process of labor unions is relatively autonomous from the influence of management and the state, and argues that management and the state may influence the very way that the internal politics of unions develops.