Gethin left the North West Frontier in May 1924 to become AQMG at the HQ of the Southern Command at Poona (map). His promotion to colonel (antedated to 1921) came in February 1924 and in June he was transferred to Army HQ as AQMG under the director of Movements and Quartering. From April to November 1925 he was Deputy Director of Pay and Pensions. He then became Assistant Adjutant General to the Directorate of Organisation, India, where two years later he became Director.
He finally left India in April 1928 and had an interlude on half pay
Gethin next took command of 160 (S Wales) Infantry Brigade in the Welsh Territorial Division in January 1929. From May 1931 until July 1933 he commanded 9th Infantry Brigade at Portsmouth, of which 2nd S.W.B. formed a part; he was promoted Major General in April 1933. After another short break he became Major General in charge of Administration in March 1934, which post he held until his retirement in 1938. Meanwhile, from 1931 until 1944 he served as Colonel of the S Wales Borderers. He was made a CB in 1934, the year he became Major General in charge of Administration, Eastern Command from which he retired in 1938. He was re-employed as Major General in charge of Administration 1939-1940. Despite all his other responsibilities he devoted considerable time to his duties as Colonel of the S Wales Borderers and was responsible for settling a long-running dispute over the Regimental Colours. In 1939, he and Ethel were living at 339 Jersey Road, Heston and Isleworth, Middlesex, with one resident servant.