Corps area

A corps area was a geographically-based organizational structure (military district) of the United States Army used to accomplish administrative, training, and tactical tasks from 1920 to 1942. Each corps area included divisions of the Regular Army, Organized Reserve, and National Guard of the United States. Developed as a result of serious mobilization problems during World War I, this organization provided a framework to rapidly expand the Army in times of war or national emergency, such as the Great Depression.

The nine corps areas, created by the War Plans Division under authority of United States War Department General Order No. 50 on 20 August 1920, had identical responsibilities for providing peacetime administrative and logistical support to the army's mobile units as was provided by the six territorial "Departments" they replaced. In addition, the corps areas took on the responsibilities for post and installation support units ("Zone of the Interior" units) created during World War I. Corps areas had the added responsibility for planning and implementing mobilization plans for all Regular Army, National Guard, and Organized Reserve mobile units in their respective geographic areas; the development and administration of hundreds of new Organized Reserve and Reserve Officers Training Corps (ROTC) units; and managing the personnel records for thousands of Reserve officers, enlisted personnel, ROTC cadets, and Citizens Military Training Camp (CMTC) candidates.

To create the corps areas, the United States was divided geographically by state lines, making nine multi-state areas that were all roughly equal in population. Each corps area was responsible for organizing two tactical corps, consisting of three infantry divisions each. Each corps area also had responsibility for organizing various other field army, General Headquarters Reserve, Zone of the Interior (later designated as Corps Area Service Command), and Communications Zone units. The First, Second, Third, Fourth, Eighth, and Ninth Corps Areas also organized units to man various fixed coastal defenses. The corps areas were further grouped into three army areas of two field armies each.

For the century preceding 1920 the U.S. Army was geographically divided into series of Military Divisions, "Departments" and smaller "Districts" and Subdistricts. Departments and divisions were numbered or named for their geographic location. Before the War of 1812 these administrative units were geographically named starting with the Department of the East and Department of the West. About 1815, the areas were numbered until after the Civil War. After the Civil War, the system used until after World War I was again geographically identified; i.e. Department of the East or Department of the Missouri and subordinate units were called divisions or districts. The last reorganization of departments was done in 1917 after the beginning of World War I.

Authorized by the National Defense Act of 1920, which amended the National Defense Act of 1916, nine multi-state sized "corps areas" were established on 20 August 1920 by the U.S. Army Chief of Staff through War Department General Order Number 50. The corps areas were formed for administration, training, and tactical control of the army, replacing the six geographical (or territorial) military departments into which the continental United States had been divided since 1917 and with little variation since the Civil War. Three overseas commands: the Hawaiian Department, Panama Canal Department, and the Philippine Department continued to be identified as departments.

The 1920 act was a realization that the mobilization of a citizen army could no longer meet the defense needs of the United States and for the first time placed an emphasis on peacetime preparedness. Yet with its passage, Congress never fully funded the program. But Congress did recognize the value of a professional officer education program by enhancing existing general service schools such as the Command and General Staff School at Fort Leavenworth, Kansas, and the Army War College at Washington Barracks, District of Columbia. The act authorized the establishing new schools to meet modern military educational needs, such as the Army Industrial College in 1924. Thirty-one additional special service schools were established or improved to provide training to the various branches of the Army.

The act established the division as a basic Army unit, replacing the pre-World War I notion of the regiment in war planning. Tactically and administratively, each corps area commander was the senior army officer for his geographical area, typically functioning as a commanding general of an existing Regular Army corps or division in their area. During times of civil unrest, labor strikes, or natural disasters, corps area commanders provided Army resources needed to address the emergency.

Each corps area was allocated two "type" corps (with a standard table of organization) and six infantry divisions. The corps were numbered in accord with their corps area designation, i.e. I and XI Corps in the First Corps Area. The lower numbered corps (I through IX) consisted of one Regular Army and two National Guard divisions among the various states of the corps area. The higher numbered corps (XI through XIX) each consisted of three divisions, also assigned by state boundaries, of the newly established (but rarely funded) Organized Reserve. By 1925, in the face of steady Coolidge Administration and congressional budget cutting, the United States Army only had three active regular divisions nationwide; the remainder of its divisions, both regular and reserve components, only existed on paper.