During the
First World War, Miles served as navigator of several ships,
HMS Empress of Russia, an
armed merchant cruiser in the
Indian Ocean (1914–1915),
HMS Botha, a
cruiser in the
Grand Fleet (1915–1916) and
HMS Fearless, a
light cruiser in the Grand Fleet (1916–1919). In 1919, he received a promotion to
lieutenant-commander. he was also appointed the Squadron Navigating Officer (Destroyers) in the
Mediterranean Fleet. He was then assigned to the operations staff of the 3rd Battle Squadron in the Mediterranean (1925–1926) and then to the staff of the Vice-Admiral Commanding 1st Battle Squadron & Vice-Admiral Second-in-Command, Mediterranean Fleet. He served in this capacity aboard the
battleship HMS Barham from 1926 to 1927. From 1931 to 1932, he commanded the
minesweeper HMS Pangbourne, then served as assistant director and acting director of the RN Staff College at Portsmouth from 1933 to 1935. Appointed as Captain (D)
3rd Destroyer Flotilla (Mediterranean) and as Commanding Officer,
HMS Codrington in 1935, Miles served in this capacity until July 1937, when he was assigned to the RN Tactical School at Portsmouth aboard
HMS Victory. He first served there as assistant director (1937–1938) and subsequently as director (1938–1939). ==Wartime==