 Walker became one of many officers holding wartime commissions to receive a commission in the Regular Army , into which he was commissioned as a first lieutenant on 1 July 1920 , but was subsequently reduced in rank to second lieutenant on 15 December 1922 , another common occurrence in the aftermath of World War I when the wartime army was demobilized . Already a command pilot , he also qualified as a combat observer in 1922 . He was promoted to first lieutenant again on 24 July 1924 . 
