 Walker joined the United States Army in 1917 , after the American entry into World War I. He trained as an aviator and became a flying instructor . In 1920 , after the end of the war , he received a commission in the Regular Army . After service in various capacities , Walker graduated from the Air Corps Tactical School in 1929 , and then served as an instructor there . He supported the creation of a separate air organization that is not subordinate to other military branches . He was a forceful advocate of the efficacy of strategic bombardment , publishing articles on the subject and becoming part of a clique known as the " Bomber Mafia " that argued for the primacy of bombardment over other forms of military aviation . He advanced the notion that fighters could not prevent a bombing attack . He participated in the Air Corps Tactical School 's development of the doctrine of industrial web theory , which called for precision attacks against carefully selected critical industrial targets . Shortly before the United States entered World War II , Walker became one of four officers assigned to the Air War Plans Division , which was tasked with developing a production requirements plan for the war in the air . Together , these officers devised the AWPD @-@ 1 plan , a blueprint for the imminent air war against Germany that called for the creation of an enormous air force to win the war through strategic bombardment . 
