The history of espionage stretches back over millennia, yet it has largely been forgotten. This book sets out to recover that lost history, to demonstrate the role of intelligence in Global events and to challenge histories which have so overlooked the intelligence dimension. The secret world is a gripping account of spies, secrets and espionage through the centuries, tracing the shift in the ancient world from divination to the gathering of real intelligence in the conduct of military operations and charting its development in statecraft through, amongst others, Renaissance Venice, Elizabethan England, Ancien régime France, revolutionary America and Tsarist Russia - right up to the sophisticated modern activities of which Christopher Andrew is the world's leading historian. What difference have security and intelligence operations made to course of history? Why have they so often forgotten by later practitioners? This fascinating book provides the answers.