Japan's first attempt to form a national-level labour organisation was the Yūaikai (Friendship Society) formed in 1912. By 1920 it had 30,000 members in 120 affiliated unions under its wing. Its philosophy was influenced by Christian unitarianism, and it was moderate and cooperative in its attitudes to management. In 1921 it became the Japan Federation of Labour (Nihon rōdō sōdōmei, Sōdōmei), which became the vehicle of one important strand of unionism, that based on the principle of labour-management co-operation. The 1920s saw a great expansion of unionism, and in 1931 there were 370,000 members of 818 unions, though this represented only 8 per cent of the total workforce.
The decade, however, was turbulent and saw the influence, first of syndicalism, then more lastingly of Marxism, penetrate the union movement. Between 1925 and 1927 Sōdōmei split three ways, the most left-wing fragment, the Japanese Council of Labour Unions (Nihon rōdō kumiai hyōgikai, Hyōgikai) being Marxist-influenced. From this period close links developed between union groups and political parties of Socialist or social democratic persuasion. Just as the party divisions formed in the 1920s carried over into the post-war period, so did parallel divisions between union groups and their ideologies. During the 1930s the union movement came under increasing pressure from a repressive militaristic State, the Marxist left was driven underground, and the moderates were forced to move further and further to the right. The scope for union activity was rapidly reduced, and in 1940 the Government banned independent unions and formed the Patriotic Industrial Association (Sangyō hōkokukai, Sanpō) as a State-run labour front.
The end of the war in 1945 and the advent of the Allied Occupation created unprecedented opportunities for union organisation. The Labour Union Law (Rōdō kumiai hō) went into effect in April 1946, ensuring for workers the rights of organisation, collective bargaining and of strike. Further legislation was passed, over the next year, to create a framework for the settlement of labour disputes, and to guarantee minimum conditions of work for workers as a whole. The MINISTRY OF LABOUR was set up in August 1947. Growth of union membership was spectacular. By 1949 around seven million workers (50 per cent of the workforce outside agriculture) had joined some 35,000 unions grouped into various federations.
The rapid growth of unionism soon began to cause problems to which the Occupation authorities reacted. Their own experience back home made it difficult for Americans to understand the profoundly political nature of Japanese labour unionism. But that was logical enough in Japanese terms, given the endemically oppressive nature of the pre-war Japanese State. Left-right ideological differences carried over from the pre-war period were intensified in the heady atmosphere of democratic opening that followed the war. At national level the movement was divided between the right-of-centre Sōdōmei federation and the left-wing,