Keegan was born in Clapham, the son of an Irish Catholic family. His father served in the First World War.

At the age of 13 Keegan contracted orthopedic tuberculosis, which has subsequently affected his gait. The long-term effects of his tuberculosis rendered him unfit for military service and the timing of his birth made him too young for service in World War II, as mentioned in his works as an ironic observation on his profession and interest. The illness also interrupted his education during his teenage years; however, his education included a period at King's College, Taunton and two years at Wimbledon College leading to entry to Balliol College, Oxford, in 1953. Following graduation he worked at the American Embassy in London for three years.

In 1960 he was appointed to a lectureship in Military History at the Royal Military Academy Sandhurst, the training establishment for officers of the British Army. Holding the post for 26 years, he became senior lecturer in military history during his tenure. During this period he also held a visiting professorship at Princeton University and was Delmas Distinguished Professor of History at Vassar College.

Leaving the academy in 1986 Keegan joined the Daily Telegraph as a Defence Correspondent and remains with the publication as Defence Editor, also writing for the American conservative website, National Review Online. In 1998 he wrote and presented the BBC's Reith Lectures, entitled War in our World.

Keegan was made an Officer of the Order of the British Empire (OBE) in the Gulf War honours list and later, in the Millennium honours list, he was knighted.

He was elected a Fellow of the Royal Society of Literature in 1986.

Keegan's books include a traditional battle-by-battle coverage of conflict, experience of the individual, historical causes of military events, technological change in warfare, military strategy, and challenges of leadership. He writes mainly for the educated non-specialist reader. Those who wish to sample his straightforward histories of war should read his histories of the Second World War and, more recently, of the First World War.

His work examines warfare throughout history, including human prehistory and the classical era; however the majority of his work concentrates on the 14th Century onwards to modern conflict of the 20th and 21st Centuries.

In A History of Warfare, Keegan outlines the development and limitations of warfare from prehistory to the modern era. It looks at various topics, including the use of horses, logistics, and "fire". One key concept put forward is that war is inherently cultural. In the introduction, he rigorously denounces the idiom "war is a continuation of policy by other means", rejecting on its face "Clausewitzian" ideas.

He has also contributed to work on historiography in modern conflict. With Richard Holmes he wrote the BBC documentary Soldiers, a history of men in battle.

Frank C. Mahncke wrote that Keegan is seen as being "among the most prominent and widely read military historians of the late twentieth century". In a book-cover blurb extracted from a more complex article, Sir Michael Howard wrote, "at once the most readable and the most original of living historians".

His book, Fields of Battle: The Wars for North America, which gives accounts of many of the wars fought on the soil of North America, also contains opening and closing essays on his own personal relationship to America. He has continued his interest in American military history with the publication of his book The American Civil War (2009, Hutchinson).

An article in the Christian Science Monitor calls Keegan a "staunch supporter" of the Iraq War. The article quotes Keegan: "Uncomfortable as the 'spectacle of raw military force' is, he concludes, that the Iraq war represents 'a better guide to what needs to be done to secure the safety of our world than any amount of law-making or treaty-writing can offer.' " He frequently justifies the war by making comparisons between it and other, more popular wars, such as both World Wars and the Napoleonic Wars.

Keegan has also been criticised by peers, including Sir Michael Howard and Christopher Bassford 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. Keegan is described as "profoundly mistaken" and Bassford states that "Nothing anywhere in Keegan's work – despite his many diatribes about Clausewitz and 'the Clausewitzians' – reflects any reading whatsoever of Clausewitz's own writings." The political scientist Richard Betts has also criticized Keegan's understanding of the political dimensions of war, writing that Keegan is "a naïf about politics."

• Barbarossa: Invasion of Russia, 1941 (New York, 1971) ISBN 0-345-02111-8
• Opening Moves - August 1941 (New York: Ballantine, 1971) ISBN 0-345-09798-X
• The Face of Battle (London, 1976) ISBN 0-670-30432-8
• Six Armies in Normandy (1982) ISBN 0-14-005293-3
• Zones Of Conflict: An Atlas Of Future Wars with Andrew Wheatcroft (New York, 1986) ISBN 0-671-60115-6
• Soldiers, A History of Men in Battle with Richard Holmes (New York: Viking Press, 1986) ISBN 0-670-80969-1
• The Mask of Command (London, 1987) ISBN 0-7126-6526-9
• The Price of Admiralty (1988) ISBN 0-09-173771-0
• Who Was Who In World War II (1978) ISBN 0-85368-182-1
• The Illustrated Face of Battle (New York and London: Viking, 1988) ISBN 0-670-82703-7
• The Second World War (Viking Press, 1990) ISBN 0-670-82359-7
• A History of Warfare (London, 1993) ISBN 0-679-73082-6
• The Battle for History: Refighting World War Two (Vintage Canada, 1995) ISBN 0-679-76743-6
• Warpaths (Pimlico, 1996) ISBN 1-8441-3750-3
• Fields of Battle: The Wars for North America (1997) ISBN 0-679-74664-1
• War and Our World: The Reith Lectures 1998 (London: Pimlico, 1999) ISBN 0-375-70520-1
• The Book of War (ed.) (Viking Press, 1999) ISBN 0-670-88804-4
• The First World War (London: Hutchinson, 1998) ISBN 0-09-1801788; (New York: Knopf, 1999) ISBN 0-375-40052-4
• Winston Churchill (2002) ISBN 0-670-03079-1
• Intelligence in War: Knowledge of the Enemy from Napoleon to Al-Qaeda (2003) ISBN 0-375-40053-2
• The Iraq War (2004) ISBN 0-09-180018-8
• Atlas of World War II (ed.) (London: Collins, 2006) ISBN 0-00-721465-0 (an update of the 1989 Times Atlas)
• The American Civil War (London, Hutchinson, 2009) ISBN 978-0-09-179483-5

Notes

Sources

• Snowman, Daniel "John Keegan" page 28—30 from History Today, Volume 50, Issue # 5, May 2000.

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