Gwynn was commissioned a second lieutenant in the Royal Engineers on 15 February 1889. Promoted to lieutenant on 15 February 1892, he saw active service in West Africa 1893–94 in operations against the Sofas, and in 1897 joined the geographical section of the Intelligence Branch of the War Office. Following the reconquest of Sudan from the Mahdi, Gwynn undertook survey work there, remaining until 1904. He was promoted to captain on 15 February 1900, received a brevet promotion to major on the following day, and was appointed a Companion of the Order of St Michael and St George for his survey work determining the Sudanese/Abyssinian border. He attended the Staff College, Camberley from 1905 to 1906. In June 1911, he was detailed to Australia as an instructor at the Royal Military College, Duntroon, where he served as the director of military art, instructing cadets in tactics, strategy and military history, with the local rank of lieutenant colonel. During much of his time there he acted as Commandant while the head of the College, Brigadier General W.T. Bridges, was away on tour. With the outbreak of World War I, he returned to England, where he unsuccessfully sought a posting to France. In July 1915, he was sent to the Middle East and was appointed General staff Officer Grade 1 of the Australian 2nd Division at Gallipoli. He was eventually posted to serve as the Chief of Staff of the II Anzac Corps, a position he held until the end of the war. He was present at the battle of Messines in June 1917. His brother, Stephen, and Stephen's son, Dennis, also served in the Great War. Gwynn was appointed a Companion of the Order of the Bath in 1918. During the Great War he was mentioned in dispatches six times, received the brevet ranks of lieutenant-colonel and colonel, and was awarded the Belgian Croix de Guerre and the French Légion d'honneur. After World War I, he served in a variety of staff assignments, culminating in May 1926 when he was made Commandant of the Staff College, Camberley. Upon his retirement in 1931, he was appointed a Knight Commander of the Order of the Bath.
Later life
After his retirement, in 1934, Major General Gwynn wrote Imperial Policing, now regarded as a classic in the field of low intensity conflict and small wars.
Family
In 1904 Gwynn married Mary Armstrong, widow of Lieutenant Lowry Armstrong of the Royal Navy. Molly Gwynn had a daughter by her first husband, named Margery Armstrong. Charles Gwynn had no children. Molly Gwynn died in 1951. Charles Gwynn spent his final years in Dublin, where he died in 1963 at the age of 93.
Personal characteristics
Gwynn was of medium height and wiry in build. He had a slight stammer.
