The first problem was that of man power. During the preceding year all sources which could be tapped without trenching upon the essential supplies of the allied armies and the nation had been exhausted, and the question had narrowed itself down to that of finding substitutes for fit men of military age still engaged in industry. An attempt was, therefore, made to enroll a large army of volunteers to take the place of the men called to the army. Partly owing to difficulties in withdrawing labor from the great war industries and partly owing to the limited supply of labor, great obstacles presented themselves in the execution of this scheme. But though the plan of enrolling an army of industrial volunteers had eventually to be abandoned the system of dilution and substitution was steadily carried out, and 820,646 men of all categories were taken for the service of the army during the year. The needs of the army, however, were not the only drain. A large amount of additional labor was required for agriculture, timber production, and iron ore mining, as well as for industrial purposes. The needs in these respects also were gradually supplied by reducing unessential industries and by organizing supplies of soldier, civilian, and foreign labor. Investigations were carried out as to the use of labor in different trades, and trade committees representing employers and employed were organized to deal with economy of man-power in particular industries. The evidence so obtained, while it demonstrated clearly the complexity and difficulty of a system of compulsory national service in industry, made it clear that in order to effect the best strategic use of the man power of the country, the National Service Department required extension rather than restriction. Accordingly, in August, 1917, the department was reorganized as a Ministry, recruiting was transferred from the War Office, and arrangements were made to insure effective co-operation between the Ministry and the employment exchanges for the period of the war. Munitions