For purposes of administration and control under war conditions the mobile land forces are organized into Field Armies, the basis of the organization being the Division. The division as prescribed in the United States Army is an organization containing all of the arms and services necessary for independent action.
A field army may be divided into army corps, each such being composed of two or more divisions.
Divisions are subdivided into brigades, which are in turn subdivided into regiments. A regiment of infantry is usually composed of three battalions of four companies each; a regiment of cavalry of three squadrons of four troops each; and a regiment of field artillery of two battalions of three batteries each. Engineers are formed into regiments according to the special requirements of their duties. The Coast Artillery is organized into companies, the number of companies in any one command depending upon the size of the forts to be garrisoned.
Signal Corps troops are organized into companies and larger organizations according to the duties assigned to them.
The Quartermaster Corps is charged with providing the supplies required and with the transportation of both men and supplies.
The Medical Corps has charge of the hospitals and the personnel required by them both at the permanent stations and in the field, and for this purpose the corps is organized into ambulance companies and field hospitals.
Chaplains are assigned to regiments and other organizations as may be required.
Veterinarians, who are commissioned officers, are assigned to the cavalry, field artillery and quartermaster transport trains, and also have charge of such veterinary hospitals as may be required at permanent posts or in the field.
The command of the Army is exercised by the President as Commander-in-Chief through the medium of the Secretary of War and the Chief of Staff, the latter officer having the rank of General and taking the place of the former Commanding General of the Army.
The General Staff Corps of the Army, consisting of commissioned officers detailed from the various branches of the Army for a term of four years’ service, is charged with the duties of effecting under the direction of the Chief of Staff the coordination and harmonious cooperation of all branches of the military service, both line and staff, in the execution of the military policies of the Government in peace and war.