on 15 January 1897 and served as midshipman in the cruiser HMS Royal Arthur in the Channel Fleet and then in the cruiser HMS Warspite on the Pacific Station. He was promoted to sub-lieutenant on 15 December 1901 and to lieutenant on 15 March 1904 before joining the armoured cruiser HMS Sutlej on the China Station. He attended the torpedo school HMS Vernon in 1907 and then remained there to work on the development of wireless telegraphy. Somerville served in the Royal Navy in the First World War, initially as a wireless officer in the battleship HMS Marlborough in the Grand Fleet and then as fleet wireless officer for the Mediterranean Fleet serving in the battleship HMS Queen Elizabeth, then the battlecruiser HMS Inflexible and then the cruiser HMS Chatham. In HMS Chatham he was involved in providing naval support for the Gallipoli Campaign. He was promoted to commander on 31 December 1915, and awarded the Distinguished Service Order and Mentioned in Despatches on 14 March 1916. He transferred to the battleship HMS King George V in the Grand Fleet in January 1917 and then joined the signals school at Portsmouth at the end of the year. Somerville stayed in the service after the war, becoming Executive Officer in the battleship HMS Ajax in the Mediterranean Fleet in March 1920 and then Executive Officer in the battleship HMS Emperor of India also in the Mediterranean Fleet. Promoted to captain on 31 December 1921, he joined the Admiralty as Deputy Director of Signals in early 1922, before becoming Flag Captain to Sir John Kelly, commanding the 4th Battle Squadron, in the battleship HMS Benbow in August 1922. He returned to the Admiralty as Director of Signals in February 1925 before becoming Flag Captain to Sir John Kelly in his new role as Commander of the 1st Battle Squadron in early 1927, first in the battleship HMS Warspite and then, after the Warspite struck a rock, in the battleship HMS Barham. He joined the directing staff at the Imperial Defence College in 1929 and became commanding officer of the cruiser HMS Norfolk in the Home Fleet in December 1931. Promoted to commodore on 14 October 1932, he became commander of the Royal Navy Barracks at Portsmouth later that month and then, after promotion to rear admiral on 12 October 1933, he became Director of Personnel Services at the Admiralty in May 1934.