During the Second World War, the number of workers who were employed by colliery companies had increased. They worked under the supervision of skilled workers who had served for long term and had come to hold the positions of the superintendent. After the defeat of W.W. II, the workplaces of colliery companies were out of order. Labor unions which had been organized rapidly beared the responsibility to maintain the order of workplaces and to control the workers. As a result, they were permitted to participate in management. Since 1949 when controls over coal-mining industry was removed, colliery companies attempted to cut down expenses and to raise efficiency. For they tried to deprive of vested rights of labor unions, many labor-management disputes took place. Red purge that was carried out at 1950 gave a blow to unions. However, managements could not succeeded in their attempts, and labor unions keeped their powerful positions to determine the labor conditions and the treatment of individual worker. In 1950's, coal mine workers improved their stability remarkably. They and their families came to live inside each coal mine in which they were employed. As a result, a feeling of identification with local community was held in common by them.