This whole situation changed radically after the outbreak of the World War. The rapid improvement in business and rise in pro ductive activity, the steady absorption of the unemployed in face of the cessation of immigration, the further stringency in the labour market after the American entry into the war, the rising levels of prices and of wages, were all factors contributing to the strength of organized labour. The membership of trade unions, consequently, nearly doubled from 1915 to 1920 and unionism won a place for the first time in the textile industry, packing houses, in machine shops, among the shop men and unskilled on the railroads, in the clothing industries and among many clerical occupations. Only in the iron and steel industry did the labour movement fail to make effective progress.
The war gains were not held. The liquidation of the war indus tries, the depression of 1921, and the revulsion in industry against organized labour caused the unions to lose 1,500,000 members by 1923. In spite of good business and employment, the losses con tinued through the decade. The severe depression of 1930 further weakened the labour movement and left it in 1933 with less than 3,000,00o members. A series of events beginning in 1933 marked a turning point in the history of American organized labour. With the election of Franklin D. Roosevelt, the labour policy of the Federal Government was radically revised. New laws were en acted to encourage organization and various administrative agen cies of the Government used their influence and power to promote union growth. These developments, together with the recovery in business and the rise of the C.I.O., brought almost immediate results. Union membership began to climb and reached 4,000,000 in 1936. Although the rivalry between the A.F. of L. and the C.I.O. makes it difficult to obtain accurate figures of union mem bership in these last years, it may be estimated that close to 6,000, 000 were members of unions in 1939. Not only is this the largest membership ever recorded in the United States, but the unions have for the time being established themselves in a greater num ber of industries and occupations than ever before, with the result that the unorganized industrial area has substantially shrunk.
All labour movements suffer from the internal dissension that arises out of clash of doctrine. Sooner or later the holding of a new view of the purposes of the labour movement grows into an attempt to capture the movement and to convert it to this view. Mild beginnings in this direction have usually ended in hitter warfare and in the disruption of one or more unions. Such was the early history of the relations between the labour movement and the socialists; after 1905 between the I.W.W. and the American Federation of Labor; and since 1918 between the communist movement and the established trade unions. In the clothing industry, for instance, the struggle for control waged during the past few years between the communist Workers' Party and the administration of several of the unions in this industry has resulted in nearly destroying organizations that were only a few years back among the most effective in the country.
Before 1933 American unions were handicapped by their uncer tain and unfavourable legal status. The free use of injunctions in labour disputes, prohibitions against interference with interstate commerce, and the "yellow-dog" contract were the devices which hindered union expansion. Virtually all of the existing disabilities, legal and political, were swept away by the legislation supported by the Roosevelt administration. Beginning with the National Industrial Recovery Act and culminating in the National Labor Relations adopted in 1935, the right to organize was strength ened and the powers of employers drastically limited. Decisions by the U.S. Supreme Court in 1937 upheld the constitutionality of the Labor Relations Act and in the process re-defined the mean ing of interstate commerce, greatly enlarged the authority of the Federal Government in dealing with labour relations, and sanc tioned many hitherto illegal union practices. The upshot of all this was a revival of trade unionism. Even the schism in the labour movement failed to arrest the spread of organization. For the C.I.O. and the A.F. of L. competed against each other, organ ized more vigorously than they would otherwise have done, and both managed to make considerable gains. Before the attacks of union organizers and decisions of the National Labor Relations Board outstanding non-union strongholds, such as the U.S. Steel and General Motors corporations, fell. Machine tenders, un skilled and agricultural labour, white-collar workers, traditionally considered unorganizable, joined unions in large numbers and through their unions won contracts with employers.