Author of some twenty penetrating books on military history, the eminent historian John Keegan turns his considerable gifts on the history of military intelligence. Although intimate knowledge of an enemy has played a role in almost every historical conflict, intelligence is often underdeveloped, misused, and misunderstood. Keegan examines a range of war experiences to show why intelligence is not always a critical element in great battles. With sensitivity and narrative verve, Keegan recounts crucial military incidents where intelligence has played a part, including Horatio Nelson's misguided chase of the French fleet up and down the Mediterranean, Stonewall Jackson's remarkable campaign in the Shenandoah Valley, and the nail-biting endeavor to crack the Enigma ciphers during World War II.