 Walker returned to the United States in February 1925 and was posted to Langley Field , where he became a member of the Air Service Board . He served successively as adjutant of the 59th Service Squadron , commander of the 11th Bombardment Squadron , and operations officer of the 2nd Bomb Group there . In June 1929 he graduated from the Air Corps Tactical School , where he studied under Captain Robert Olds , a former aide to air power pioneer Billy Mitchell and a passionate advocate of strategic bombing . He then served at the Air Corps Tactical School as an instructor under Captain Olds in the Bombardment Section until July 1933 , both at Langley and at Maxwell Field , where the school was relocated in 1931 . Walker became part of a small clique of Air Corps Tactical School instructors that became known as the " Bomber Mafia " , that argued that bombardment was the most important form of airpower . Its members also included Haywood Hansell , Donald Wilson , Harold L. George , and Robert M. Webster , Their influence was such that , during their tenure , bombardment achieved primacy over pursuit in the development of Air Corps doctrine . 
