Despite their fractious relationship, Mitchell and Foulois were of one mind on the necessity of forming an "air force" to centralize control over tactical aviation. In the St-Mihiel Offensive, commencing September 12, 1918, the American and French offensive against the German salient was supported by 1,481 airplanes directed by Mitchell, totaling 24 Air Service, 58 French "Aéronautique Militaire", and three Royal Air Force squadrons in coordinated operations. Observation and pursuit planes supported ground forces, while the other two-thirds of the aerial force bombed and strafed behind enemy lines. Later, during the Meuse-Argonne offensive, Mitchell employed a smaller concentration of airpower, nearly all American this time, to keep the German army on the defensive.