he completed the standard four-year period as a regimental commander on 1 May 1909, and was placed on half-pay. However the same issue, carried notice of his promotion to colonel backdated to 4 December 1912. He was seconded to the Egyptian Army, and in 1913–14 he was commandant of the Khartoum district where he was active in combating the slave trade. First World War Smyth was dispatched to Gallipoli by Lord Kitchener, arriving in May 1915. He commanded the 1st Australian Infantry Brigade as a temporary brigadier general at the Battle of Lone Pine and was one of the last officers to leave the peninsula. He was appointed Companion of the Order of the Bath (CB) on 1 January 1916, and received a further Mention in Despatches on 28 January 1916. Smyth led the brigade in France in 1916, and on 28 December was given command of the 2nd Australian Division as a temporary major general. He was Mentioned in Despatches twice more, on 15 May 1917 and 11 December 1917, and was promoted substantive major general on 1 January 1918 as a "reward for distinguished service in the field." He was transferred back to the British Army in May 1918 and briefly commanded the 58th (2/1st London) Division and then the 59th (2nd North Midland) Division from August 1918, leading the latter during the liberation of Lille in October 1918. He had learned to fly in 1913 and was known for borrowing aircraft to look at the lines for himself. He was yet again Mentioned in Despatches on 20 December 1918. Smyth was promoted Knight Commander of the Order of the Bath (KCB) in the 1919 King's Birthday Honours. On 30 July 1919 was appointed General Officer Commanding 47th (1/2nd London) Division (Territorial Force). During the war he had also been awarded the Belgian Croix de Guerre, and the French Legion of Honour in the grade of Officer. In all, he was Mentioned in Despatches eleven times during his career. He was appointed colonel of the 3rd Dragoon Guards on 1 October 1920. He relinquished command of his division on 30 July 1923. Smyth retired from the British Army on 5 July 1924, and relinquished the colonelcy of the 3rd Dragoon Guards on 16 October 1925. Smyth served as the Honorary Colonel of the South African Natal Carbineers from 1920 to 1925 and then of the 37/39 Battalion, Australia.