7. 故用間有五有鄉間有內間有反間有死間有生間
Hence the use of spies, of whom there are five classes: (1) Local
spies; (2) inward spies; (3) converted spies; (4) doomed spies; (5)
surviving spies.
Sun Tzŭ on the Art of War: The Oldest Military Treatise in the World · 第 420 / 458 题