Sir Charles Edward Callwell (1859-1928) was an Irish author, intelligence officer and linguist. For his essay on British army operations since 1865 he was awarded the Royal United Service Institute gold medal. The essay became the basis for his most well-known work; Small Wars: A Tactical Textbook for Imperial Soldiers, first published in 1896. Amongst his other works are Military Operations and Maritime Preponderance (1905) and Experiences of a Dug-out, 1914- 1918 (1920). He was Director of Military Operations at the War Office during the First World War.