Only one factor among many

This is a fascinating book on a fascinating subject, written by a master of his craft as a military historian. Sir John Keegan’s declared purpose is to answer a simple question: ‘How useful is intelligence in war?’ The answer he gives is that, however useful intelligence is in disclosing the enemy’s intentions, strengths and weaknesses, wars are won not by knowledge but by brute force in battle. The modern fad to give primacy to knowledge he rejects as misleading. Addicts of spy fiction will be disappointed. Spies rarely supply relevant information in time for it to be of use. This book is not cloak and dagger stuff but a superbly researched series of case studies on the use of intelligence in war from the 18th century to the present war against terrorism.

Keegan’s first case study is Nelson’s 73 weeks’ chase, backwards and forwards across the Mediterranean, of Napoleon’s fleet in 1798.