Keegan is a British historian. 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 1960, Keegan was appointed to a lectureship in Military History at 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 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 and Our World?.
Keegan was made an Officer of the Order of the British Empire, styled OBE, in the gulf war honours list and later, in the Millennium honours list, advanced to be a Knight Commander, styled KBE and entitled to use the honourific Sir.
Source - http://en.wikipedia.org/wiki/John_Keegan