Guard, and the Organized Reserves, all so organized and trained as to provide the framework on which the required man-power of the nation is mobilized, trained, armed, equipped, and supplied, and the necessary resources of the nation are organized. In addition, provisions exist for voluntary partial training of a part of the young men of the nation by brief and intensive training camp courses and by training in high schools, colleges, and universities throughout the country. The agencies for voluntary military training include at present, the Reserve Officers' Training Corps and the Citizens' Military Training Camps.
3. Land Forces.—The military forces of the United States consist of all citizens of the United States, male and female, who are able to render military service in any capacity, direct or indirect, as combatants or non-combatants. The organized land forces of the United States consist of the Regular Army, the National Guard, and the Organized Reserves. These three components of our military forces have a common mission—elements welded into an harmonious and efficient whole—and constitute the Army of the United States. The Regular Army, the National Guard, and the Organized Reserves form, respectively, the first, second, and third echelons of this army. These are coordinated echelons, and each reinforces the other. They will not be used as replacements one for the other, except in the case of unassigned officers of the Organized Reserves, who may be assigned to the Regular Army. Each echelon is distinct in its status and each has a specific mission, but at the same time is a necessary and correlated part of the national military system. In an emergency requiring the maximum mobilization, the three echelons will furnish six field armies, each army consisting of two cavalry divisions and three corps each composed of three divisions. In addition to the field armies, each echelon will supply its pro rata share of the General Headquarters Reserve units, and of the personnel necessary for the communications zone and the zone of the interior. Of the six field armies the Regular ARmy will furnish one, the National Guard two, and the Organized Reserves three. This scheme of mobilization contemplates, in principle, the initial employment of each echelon in succession, but ultimately combines them into
