Scoones was born in Karachi, British India, the eldest son of Fitzmaurice Thomas Favre Scoones of the Royal Fusiliers and his wife, Florence Osborne, who was born in New South Wales, Australia. His younger brother was Sir Reginald "Cully" Scoones. In 1901 Scoones, with his father, his mother, and his brothers Thomas, Valentine, and Reginald, lived in the parish of Heston, in Hounslow, Middlesex, England, at The Hermitage, Sutton Lane. His father was posted to the Bermuda Garrison with the 3rd Battalion the Royal Fusiliers, arriving aboard the troopship Dominion at the start of December 1903, along with Major CJ Stanton, Lieutenant F Moore, and Second-Lieutenant George Ernest Hawes of the same battalion. The battalion was first posted to Boaz Island. His father was subsequently appointed Camp Commandant, Warwick Camp. The 3rd Battalion departed from the Royal Naval Dockyard, Bermuda, aboard the troopship Kensington on 13 October, 1905, for Aldershot. Scoones was educated at Wellington College and the Royal Military College, Sandhurst.
Scoones was commissioned a second lieutenant on the unattached list for the Indian Army on 20 January 1912. He was accepted into the Indian Army and appointed to the 2nd Battalion 2nd Gurkha Rifles on 8 March 1913. He was promoted to lieutenant on 20 April 1914. He saw active service in the First World War, becoming aide-de-camp to the Commander of Meerut Division, then aide-de-camp to the commander 21st Division and finally aide-de-camp to the Army Corps Commander, 2nd Army Corps in France, between 8 September 1915 and 10 July 1917. Promoted to captain on 20 January 1916, he became a brigade major in India on 27 October 1917. He was mentioned in despatches three times and awarded the Distinguished Service Order and the Military Cross. After the war, Scoones saw service during the Afghanistan North West Frontier operations in 1919. After attending the Staff College, Quetta from 1922 to 1923, he served as a brigade major in India from 3 March 1924 to 30 November 1926 and then became a general staff officer. Promoted to brevet major on 7 January 1925, he transferred to the 1st Battalion 2nd Gurkha Rifles on 22 January 1928 He was promoted to major on 20 January 1929, and to brevet lieutenant colonel on 1 January 1933. After attending the Imperial Defence College, from 14 February 1935 to 23 April 1938 he was made Commanding Officer of the 2nd Battalion the 8th Gurkha Rifles. He was appointed an Officer of the Order of the British Empire for earthquake work at Quetta in 1935.
Scoones served in the Second World War initially as a general staff officer on the Directorate of Military Operations and Intelligence. On 17 May 1940 he was appointed deputy director of military operations, India. The following year, he became director of military operations and intelligence, India. In 1942, Scoones briefly commanded the Indian 19th Infantry Division before being promoted to lieutenant-general and appointed to command IV Corps, part of William Slim'sFourteenth Army. This Corps defended Imphal in Manipur, on the frontier between India and Japanese-held Burma. It also had responsibility for a large rearguard area, and a very large tract of unmapped and trackless jungle-covered frontier. He was appointed a Companion of the Order of the Star of India in 1942. Scoones commanded the corps through the gruelling Battle of Imphal. In December 1944 he and his fellow corps commanders Stopford and Christison were knighted and invested as Knights Commander of the Order of the British Empire by the viceroy Lord Wavell at a ceremony at Imphal in front of the Scottish, Gurkha and Punjab regiments. Slim was knighted and invested as Knight Commander of the Order of the Bath at the same occasion. Slim valued Scoones as a defensive commander, but when the Fourteenth Army went onto the offensive after Imphal he wanted a more aggressive and less calculating commander for IV Corps. Scoones was appointed to Central Command, India.
