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 &lt;a href="58th%20%282/1st%20London%29%20Division"&gt;58th (2/1st London) Division&lt;/a&gt; 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.