In 1914, Leslie joined the 2nd London Regiment and was posted to Egypt. He became ill with Mumps and was hospitalised on the Island of Malta. He saw service in Egypt and Gallipoli before being posted to the Western Front in April 1916. Leslie was transferred to the 12th (County of London) Battalion (The Rangers) and was wounded at the Battle of Le Transloy on The Somme on 7th October 1916.
He died of his wounds on 8th October 1916 and was buried in Grove Town Cemetery, Méaulte, Picardie, France. At the time of his death, Leslie held the rank of Sergeant.
Leslie Coulson’s WW1 poetry collections were:“From an outpost, and other poems”, published by Erskine Macdonald, London in 1917
You can read some of Leslie's poetry here:
Catherine W. Reilly "English Poetry of the First World War A Bibliography" (New York, St. Martin's Press, 1978)