Corps Area - The End of The "corps Area" Concept

The End of The "corps Area" Concept

General Douglas MacArthur, the Army’s Chief of Staff, believed that the 1921 mobilization plan was based on unsound assumptions and that the Army required active field army headquarters before the start of any mobilization to manage the integration and training of subordinate units as they mobilized. He also concluded that the existing three army area/six army arrangement was too ponderous to field a force that might be needed in a hurry and that existing mobilization plans were not flexible enough to tailor to various war plans then in existence. After a War Department study, MacArthur on 9 August 1932 constituted three new army headquarters in the Regular Army (the headquarters of the First United States Army was already constituted) and outlined the organization of what became known as the "four army" plan, which effectively abolished the three army area/six army system.

On 3 October 1940, the War Department transferred tactical command functions to General Headquarters, U.S. Army, separating the field armies from the corps areas. Corps areas were then limited to their Zone of the Interior functions as service commands and the field armies assumed control of all tactical units.

In 1942, after the start of World War II and by executive order, the army level organizations took to training or the field as home defense and combat commands under the control of Army Ground Forces. In March 1942, home defense and training activities were assigned to the newly formed Eastern, Central, Southern, and Western Defense Commands, which overlaid the existing Corps Areas. The geographical corps areas were redesigned as numbered service commands under Services of Supply, renamed in 1943 as Army Service Forces to serve the Army's supply system, and perform administration, and "housekeeping" functions within the United States in support of the war effort such as the issuance of Army serial numbers and the operation of induction centers and domestic army posts. By this time, the corps area boundaries and departments experienced some minor readjustments:

• Eastern Defense Command (co-headquartered with First Army until October 1943)
  • 1st Corps Area – ME, VT, NH, MA, CT, RI
  • 2nd Corps Area – NY, NJ, DE
  • 3rd Corps Area – PA, MD, VA, DC
  • 4th Corps Area – NC, SC, GA, FL, AL, MS, TN
• Central Defense Command (co-headquartered with Second Army)
  • 5th Corps Area – OH, IN, KY, WV
  • 6th Corps Area – IL, MI, WI
  • 7th Corps Area – MO, KS, NB, CO, IA, MN, ND, SD, WY
• Southern Defense Command (co-headquartered with Third Army until December 1943)
  • 8th Corps Area – AR, LA, TX, OK, NM
• Western Defense Command (co-headquartered with Fourth Army)
  • 9th Corps Area – WA, OR, CA, ID, MT, NV, UT, AK

• Hawaiian Department
• Panama Canal Department
• Philippine Department
• Puerto Rican Department