He served in World War I reaching the rank of Captain in the British army (36th Ulster Division). After the war he helped write several of the official British military histories of the war. Later he wrote both specialist detailed histories as well as histories intended for the normal reader. He was an expert on the history of World War I.
Books
The History of the 36th (Ulster) Division (1921) (Reprinted 1998 ISBN 978-0094783102)
Military Operations - Egypt and Palestine Vol I. From the outbreak of war with Germany to June 1917 (with Sir George MacMunn) (London, 1928) (Official History)
Military Operations - Egypt and Palestine: Vol II. From June 1917 to the end of the War (London, 1928) (Official History)
War Books (1930)
Military Operations - Macedonia: Vol I. From the Outbreak of War to the Spring of 1917 (London, 1933) (Official History)
Military Operations - Macedonia: Vol II. From the Spring of 1917 to the end of the war (London, 1933) (Official History)
Marshal Foch (London, 1939)
Military Operations - France and Belgium,1917: Vol I, The German Retreat to the Hindenburg Line and the Battles of Arras (London, 1940) (Official History)
Military Operations, France and Belgium, 1917: Vol II, The German Retreat to the Hindenburg Line and the Battles of Arras Cyril Falls, Cyril Bentham Falls, Archibald Frank Becke, James E. Edmonds. (London, 1940) Macmillan reprinted 1992 ISBN 0-901-62790-9