Masterman started his service career in the
Royal Navy, attending the
Britannia Naval College around 1894. He served on in the late 1890s and early 1900s, and was promoted to
lieutenant in January 1900. After attending Torpedo Specialist Course he in 1907 worked as a Russia interpreter on . By 1911 Masterman had become involved in the Navy's efforts to build an experimental
airship and the following year he was appointed Officer Commanding the Naval Airship Section. During the
First World War, Masterman served in the
Royal Naval Air Service, commanding the Farnborough Airship Station and working in several technical posts; during this time he invented and patented the airship
mooring mast with
Barnes Wallis. With the establishment of the
Royal Air Force on 1 April 1918, Masterman transferred to the new service. Just before the end of the war, he was promoted to
brigadier general and appointed
General Officer Commanding No. 22 Group. When separate RAF ranks were introduced on 1 August 1919 he became an Air Commodore. In 1922 Masterman was appointed as Commandant of the RAF's
Central Flying School. ==Observer Corps==