In early April 1902 Forbes transferred to the armoured cruiser HMS Aboukir, also serving in the Mediterranean Fleet.[6] After attending the gunnery school HMS Excellent in 1903, he was assigned to Directing Staff at the gunnery school HMS Cambridge in June 1904.[3] He then became gunnery officer in the armoured cruiser HMS Carnarvon in the Mediterranean Fleet in May 1905 and gunnery officer in the battleship HMS Dominion in the Channel Fleet in May 1908.[7] After joining the staff of the Inspectorate of Target Practice in October 1910, he became gunnery officer in the battleship HMS Superb in the Home Fleet in February 1911 and then, having been promoted to commander on 31 December 1912,[8] he returned to the gunnery school HMS Excellent in early 1913.[7]
After the end of the war, Forbes served as Naval Member of the Ordnance Committee from October 1919 and then, after attending the Senior Officers' course at the Royal Naval War College, he served as Deputy Director of the Royal Navy Staff College from August 1921.[7] He became Flag Captain to the Commander-in-Chief of the Atlantic Fleet in the battleship HMS Queen Elizabeth in June 1923, Flag Captain to the Flag Officer Commanding the 3rd Battle Squadron in the battleship HMS Iron Duke in October 1924 and Director of Naval Ordnance at the Admiralty in June 1925.[7] He was appointed a naval aide-de-camp to the King on 12 April 1928.[12] Promoted to rear admiral on 5 October 1928[13] and appointed a Companion of the Order of the Bath on 3 June 1929,[14] he became Rear Admiral commanding the Destroyer Flotillas in the Mediterranean Fleet with his flag in the cruiser HMS Coventry in August 1930 and Third Sea Lord and Controller of the Navy in March 1932.[7] Promoted to vice admiral on 21 January 1933,[15] he became Vice Admiral commanding 1st Battle Squadron and Second in Command of the Mediterranean Fleet with his flag in the battleship HMS Revenge in April 1934.[7] Advanced to Knight Commander of the Order of the Bath on 3 June 1935,[16] he re-deployed his fleet from Malta to Alexandria to avoid attack by the Italian Navy at the start of the Second Italo-Ethiopian War in October 1935.[7] Promoted to full admiral on 19 August 1936,[17] he became Commander-in-Chief, Home Fleet with his flag in the battleship HMS Nelson in April 1938.[18]
In 1909 Forbes married Agnes Millicent Ewen; they had a son and a daughter.[7] Following the death of his first wife, he married Marie Louise Berndtson in 1921. They had one daughter; the opera critic, journalist, author, and musicologist Elizabeth Forbes.[23][1] His younger brother was ColonelOswald Boyd Forbes.[24]