The post of Chief of the Air Staff (CAS) was established in January 1918, just prior to the official formation of the
Royal Air Force (RAF), and its first occupant was Major General Sir
Hugh Trenchard. Following Trenchard's resignation in March 1918 after disagreements with the first air minister,
Lord Rothermere, his rival Major General Sir
Frederick Sykes was appointed. For political reasons Trenchard's resignation did not take effect until late April in order that he would be CAS when the RAF was formed. With
Winston Churchill's post-war appointment as
Secretary of State for War and
Air, Sykes was moved sideways to head up the nascent Civil Aviation ministry and Trenchard returned as CAS. In the early 1920s, Trenchard had to fight to keep the RAF from being divided and absorbed back into the
Royal Navy and the
British Army. After Lord Trenchard retired in 1930 there were still suggestions that the RAF should be broken up, but Trenchard's foundations proved solid. By the time the
Second World War broke out in 1939, the then occupant of the post, Air Chief Marshal Sir
Cyril Newall, had a service that had been undergoing the most rapid of expansions during the British rearmament programs of the late 1930s. Newall gave way in 1940 to Air Chief Marshal Sir
Charles Portal, who led the service for the rest of the war. Portal was a tireless defender of the RAF and highly capable in administration and strategy. After the war the RAF was reoriented to perform the dual roles of defending the shrinking
British Empire and possibly fighting against the
Soviet Union in a
Warsaw Pact verses
NATO war over Germany and the United Kingdom. The Chiefs of the Air Staff of the day had to fight a constant battle to keep the British aircraft industry alive. In the end only minimal success was achieved, with only a rump aviation industrial base left by the 1970s. The first eight Chiefs of the Air Staff were originally commissioned in the British Army, with four coming from the infantry, two from the artillery and one each from the cavalry and the engineers. Of these both Lord Trenchard and Sir
John Salmond each held the post over two separate periods. By the early mid-1950s sufficient time had elapsed for officers originally commissioned in the British air services of the First World War to have risen through the ranks to RAF's senior post; Sir
John Slessor had originally served in the
Royal Flying Corps while Sir
William Dickson was commissioned into the
Royal Naval Air Service. In 1956 Sir
Dermot Boyle became the first CAS to have originally been commissioned in the RAF. Until 2023, every occupant of the post originally commissioned in the RAF was a qualified pilot. The first non-pilot to be appointed to the role is Sir
Richard Knighton, who joined the RAF as an engineer, and who took up post in June 2023. ==Appointees==