The amended National Defense Act also grouped three corps areas into an "army level" mobilization organization whose boundaries were also identical for the two "type" armies located within them. For example, First, Second, and Third Corps Areas, and the First and Fourth (Field) Armies, comprised the First "Army Area". The 1921 mobilization planning that created the six field army headquarters did not envision a need for active field army-level commands in peacetime and thus the headquarters were constituted in the Organized Reserve rather than the Regular Army.