The only premodern contemplation of spies ever written apart from Sunzi's brief but incisive Art of War chapter, Jian Shu (Book of Spies) was completed in the last century of the severely weakened Qing dynasty to address pressing defensive needs. The first third of the book ponders the nature of clandestine intelligence gathering, including estrangement and disinformation, two crucial elements in the activist orientation that characterized China's theory and practice from the outset; agent categories and their missions; aspects of historical evolution; and the critical need for their skills despite the misgiving, even condemnation, of Confucian oriented officials. The remainder of the book consists of fifty-three historical exemplifications that show the techniques and their effects in practice. Interspersed with theoretical analysis and drawn from over 2500 years of strife and intrigue, they represent a veritable window on the practice of Chinese spycraft that remains of contemporary interest in the PRC. Ralph D. Sawyer, the translator, is a noted specialist in Chinese strategic and intelligence issues. His books on intelligence include The Tao of Spycraft: Intelligence Theory and Practice in Traditional China; The Tao of Deception: Unorthodox Warfare in Historic and Modern China; and Lever of Power: Military Deception in China and the West. His translation of important military works from China's voluminous tradition include The Seven Military Classics of Ancient China; Sun-tzu Art of War; Sun Pin Military Methods; Strategies for the Human Realm: Crux of the T'ai-pai Yin-ching; Zhuge Liang: Strategy, Achievements, and Writings; Ruminations in a Grass Hut; and One Hundred Unorthodox Strategies: Battle and Tactics of Chinese Warfare.