In the introduction, he vigorously denounced the idiom 'war is a continuation of policy by other means', rejecting ' Clausewitzian' ideas. A key concept put forward was that war is inherently cultural. It looked at various topics, including the use of horses, logistics, and 'fire'. In A History of Warfare, Keegan outlined the development and limitations of warfare from prehistory to the modern era. He was survived by his wife, their two daughters and two sons.

Keegan died on 2 August 2012 of natural causes at his home in Kilmington, Wiltshire. In 1998, he wrote and presented the BBC's Reith Lectures, entitling them War in our World. He also wrote for the conservative American publication National Review Online. Leaving the academy in 1986, Keegan joined the Daily Telegraph as a defence correspondent and stayed with the paper as defence editor until his death. He remained there for 26 years, becoming a senior lecturer in military history during his tenure, during which he also held a visiting professorship at Princeton University and was Delmas Distinguished Professor of History at Vassar College. In 1960 Keegan took up a lectureship in military history at the Royal Military Academy Sandhurst, which trains officers for the British Army. After graduation he worked at the American Embassy in London for three years. The illness also interrupted his education in his teenage years, although it included a period at King's College, Taunton and two years at Wimbledon College, which led to entry to Balliol College, Oxford in 1953, where he read history with an emphasis on war theory. The long-term effects of this rendered him unfit for military service, and the timing of his birth made him too young for service in the Second World War, facts he mentioned in his works as an ironic observation on his profession and interests. At the age of 13, Keegan contracted orthopaedic tuberculosis, which subsequently affected his gait. Keegan was born in Clapham to an Irish World War One veteran and was evacuated to Somerset when World War Two broke out. He wrote many published works on the nature of combat between prehistory and the 21st century, covering land, air, maritime, intelligence warfare and the psychology of battle.

Sir John Desmond Patrick Keegan OBE FRSL ( – 2 August 2012) was an English military historian, lecturer, author and journalist.

The Face of Battle, Soldiers: A History of Men in Battle, The Mask of Command and other major works Military history, history of warfare, First World War

The First World War by John Keegan