The General Staff produced a mobilization plan that in the event of war would create a field force of six armies, 18 corps, and 54 divisions. Each army would have an Air Service attack wing (one attack and two pursuit groups) and an observation group, each corps and division would have an observation squadron, and a seventh attack wing-observation group would be reserved for the Expeditionary Force's general headquarters. A single bombardment group was planned, relegating bombardment to the most minor of roles. All aviation units would be under the command of ground officers at all levels. While promoting unity of command within the service as its most important principle, the plan obviated concentration of forces by its air units. This structure provided the principles by which the Air Service and Air Corps operated until 1935.