Sir John Desmond Patrick Keegan OBE FRSL (15 May 1934 – 2 August 2012) was an English military historian, lecturer, author and journalist.

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.

[6] In the introduction, he vigorously denounced the notion that war is a reasonable tool of statecraft, "simply a continuation of [interstate] politics by other means", rejecting "Clausewitzian" ideas.

[9] Keegan was also criticised by peers, including Sir Michael Howard[13] and Christopher Bassford[14] for his critical position on Carl von Clausewitz, a Prussian officer and author of Vom Kriege (On War), one of the basic texts on warfare and military strategy.

MacKenzie reports Keegan as saying that the best panzer units of the Waffen SS altered the course of the war and were "faithful unto death and fiercer in combat than any soldiers who fought them on western battlefields".

[17] Detlef Siebert, a television documentarian, disagreed with Keegan's view that the deliberate targeting of civilian populations by aerial bombing 'descended to the enemy's level', although he did call it a 'moral blemish'.

[18] On 29 June 1991, as a war correspondent for The Daily Telegraph, Keegan was appointed Officer of the Order of the British Empire (OBE) "in recognition of service within the operations in the Gulf".