Field Marshal Sir Cyril John Deverell (9 November 1874 – 12 May 1947) was a British Army officer who served as Chief of the Imperial General Staff (CIGS), the professional head of the British Army, from 1936 to 1937. Prior to his becoming CIGS, he fought in the Fourth Anglo-Ashanti War and the First World War, during which he commanded at battalion, brigade and division level, and later advised the British government on the importance of maintaining the capability to mount an Expeditionary Force for operations on mainland Europe in the years leading up to the Second World War. Early life Deverell was born the son of Lieutenant John Baines Seddon Deverell and Harriet Strappini Deverell (née Roberts) and educated at Bedford School. Military career Deverell was commissioned into the Prince of Wales's West Yorkshire Regiment on 6 March 1895. He served in the Fourth Anglo-Ashanti War in 1896 and was then promoted to lieutenant on 3 August 1898. He was appointed adjutant of his regiment on 9 February 1904 before being promoted to captain on 23 February 1904. He served in the First World War initially as brigade major for 85th Brigade, in which role he joined the British Expeditionary Force (BEF) and saw action at the Second Battle of Ypres in April 1915 before being promoted to major on 3 June 1915. Deverell became Commanding Officer (CO) of the 1/4th Battalion, East Yorkshire Regiment in July 1915 and was then asked to command the 20th Brigade from 29 October 1915. Promoted to lieutenant colonel on 26 August 1916, he took part in the Battle of the Somme in the autumn of 1916. His brigade held a position on the 21st Division's right flank during the Battle of Bazentin Ridge and attacked the Switch Line to the east of High Wood. Promoted to the substantive rank of colonel and temporary major-general on 1 January 1917, Deverell was given command of the 3rd Division after its commander, Sir Aylmer Haldane, took over VI Corps. He led the division at Arras in 1917, then participated in the latter stages of the Battle of Passchendaele. He returned to the Somme in 1918, before fighting alongside the Portuguese at the Battle of the Lys. The division participated in the Hundred Days Offensive, finally leading to the German surrender on 11 November 1918. He was appointed a Companion of the Order of the Bath