Smith was the son of Lt.-Col. Andrew William Douglas Smith, Royal Marines and Myra Elizabeth Luxmoore, an artist. Smith was commissioned into the Royal Scots Fusiliers in 1885. He took part in the Burma expedition in 1886 and the Tirah Campaign in 1897. He was appointed a Brigade Major in India in 1905 and Commanding Officer of 1 Bn Royal Scots Fusiliers in 1911. He served in World War I as Commander of the 9th Infantry Brigade, as General Officer Commanding 20th (Light) Division and then as General Officer Commanding &lt;a href="56th%20%28London%29%20Infantry%20Division"&gt;56th (1/1st London) Division&lt;/a&gt; in France. He took command of the 56th Division on a temporary basis between 24 July 1917 and 9 August 1917 after his predecessor had been taken ill and until a permanent appointment could be made.