Upon the outbreak of World War I in August 1914, Miles, with his battalion, then serving in Dublin as part of the 13th Brigade of the 5th Division, was sent overseas to France, landing at Le Havre on 15 August, as part of the British Expeditionary Force (BEF). Promoted to the temporary rank of lieutenant on 27 August 1914,[6] Miles, his rank of lieutenant made permanent,[7] participated in all the major battles in which the battalion was engaged that year, beginning with the Battle of Mons and the subsequent retreat, and culminating in the First Battle of Ypres, where Miles's battalion suffered very heavy losses, although Miles himself survived unscathed and, from 18 November 1914, was seconded to the Army Signal Service.[8] During the Battle of Hill 60 in April−May 1915, Miles, while attached to the 5th Signal Company, Royal Engineers, was awarded the Military Cross (MC) on 23 July 1915. The citation read:
For conspicuous gallantry. During a critical period in the attack on "Hill 60" and neighbouring trenches on May 1st, 1915, he succeeded in mending the telephone wire along the railway cutting under such heavy shell fire that messengers were unable to get through.[9][10]
Posted to the Belgian border soon after, the German Armyinvaded France on 10 May, less than a month after the brigade's arrival, and the brigade, along with the rest of the division, was initially held in reserve until being ordered to advance to the River Escaut. On 22 May the Germans attacked the 42nd Division heavily along its entire front, and by the end of the day, after several hours of confused fighting, was ordered to retreat to Dunkirk, where the rest of the BEF, now cut off from most of the French Army further south, was already converging.[19] The brigade, after temporarily coming under the command of the 1st Division for the final stages of the fighting in the Dunkirk perimeter, was evacuated from Dunkirk on the night of 1 June, along with Miles himself, and returning to 42nd Division command the day after.[19] The brigade, during the fighting, had suffered heavy losses in both manpower and equipment, but had gained one of the first Victoria Crosses (VC) of the war, belonging to Captain Marcus Ervine-Andrews of the 1st Battalion, East Lancashire Regiment.[3]
Miles continued to command the brigade after its return to England, training it in preparation for the expected German invasion of England and at the same time absorbing conscripts to bring the brigade up to strength after its heavy casualties. He became Brigadier General Staff (BGS) of Home Forces in mid-September before returning to the 42nd Division in late April 1941, this time as its GOC, succeeding Major General Henry Willcox, who in turn had succeeded Major General Holmes the previous June, Miles in turn receiving a promotion to acting major general in May.[20][19] He was promoted to permanent major general in June.[21] The division comprised, in addition to Miles's old 126th Brigade, the 125th and 127th Infantry Brigades, and divisional troops, and was serving in Eastern Command in East Anglia as part of Lieutenant GeneralHugh Massy's XI Corps.[3] The division's main role was that of a static beach defence, and training to repel an invasion.[19]
Later in 1943, after recovering from his injury, he became GOC Kent and South East Districts and, in September 1944, as an acting lieutenant general, he took over as General Officer Commanding-in-Chief (GOC-in-C) of South-Eastern Command.[24]
Postwar
He retired from the army, after a career spanning thirty-five years, in September 1946, retaining his permanent rank of major general.[25][19] He served as Colonel of his old regiment, the King's Own Scottish Borderers, from 19 June 1944[26] until 19 June 1954.[27] He was Deputy Chairman of the LichfieldDiocesan Board of Finance from 1954 to 1960, becoming Chairman from 1960 to 1971, and became a member of the House of Laity, Church Assembly from 1955 to 1960.[19] Miles retired to Shropshire, where he lived at Tilstock near Whitchurch before moving in 1956 to his last home, Rope Walk on Lyth Hill near Shrewsbury.[28] After the death of his wife in 1972, his last five years were spent as a widower[19] before he died at Brookfield Nursing Home in Newport, Shropshire on 3 November 1977. His funeral took place at Condover, Shropshire, on 9 November.[29]