Poole attended the Royal Military Academy, Woolwich and was commissioned into the Royal Artillery in February 1889. He was promoted to lieutenant on 15 February 1892, and served in the Tirah Campaign in India from 1897 to 1898. Promotion to captain followed on 14 June 1899. Poole served in the Second Boer War in South Africa, for which he left on the SS "British Prince" in March 1900. He was attached to the ammunition column of the 8th Division, and was later in command of "P Section Pom-poms", and was present at the engagements at Botha′s Pass, the storming of Alleman′s Nek (June 1900), the Battle of Bergendal and operations near Lydenburg (August 1900). For his service, he was twice mentioned in despatches (including the final despatch by Lord Kitchener dated 23 June 1902), and was awarded the Distinguished Service Order (DSO). Following the end of the war, Poole left Cape Town for England on the SS "Simla" in July 1902. From 1903 to 1904 he was with the Somaliland Field Force and participated in the Somaliland Campaign. He then saw action in Northern Nigeria in 1904 and was promoted to major in 1909. He retired from the army in 1914.