British author and historian who specialized in military history and military biography, particularly of the Second World War. Macksey was commissioned in the Royal Armoured Corps and served during the Second World War (earning the Military Cross under the command of Percy Hobart). Macksey later wrote the (authoritative) biography of Hobart.Macksey gained a permanent commission in 1946, was transferred to the Royal Tank Regiment in 1947, reached the rank of major in 1957 and retired from the Army in 1968.

Amongst many other books, Macksey wrote two volumes of alternate history, one, entitled Invasion, dealt with a successful invasion of England by Germany in 1940 and the other describing a NATO–Warsaw Pact clash in the late 1980s. The latter book was done under contract to the Canadian Forces and focuses on the Canadian role in such a conflict. He was an editor and contributor to Greenhill's Alternate Decisions series since 1995.

In Macksey's Guderian – Panzer General, he refuted the view of historian Sir Basil Liddell-Hart regarding Hart's influence on the development of German Tank Theory in the years leading up to 1939.