[Tu Mu gives a graphic touch: all communication with spies should be carried "mouth-to-ear." The following remarks on spies may be quoted from Turenne, who made perhaps larger use of them than any previous commander: "Spies are attached to those who give them most, he who pays them ill is never served. They should never be known to anybody; nor should they know one another. When they propose anything very material, secure their persons, or have in your possession their wives and children as hostages for their fidelity. Never communicate anything to them but what is absolutely necessary that they should know. [2] ]
15. Spies cannot be usefully employed without a certain intuitive sagacity.
[Mei Yao-ch`en says: "In order to use them, one must know fact from falsehood, and be able to discriminate between honesty and double-dealing." Wang Hsi in a different interpretation thinks more along the lines of "intuitive perception" and "practical intelligence."Tu Mu strangely refers these attributes to the spies themselves: "Before using spies we must assure ourselves as to their integrity of character and the extent of their experience and skill." But he continues: "Abrazen face and a crafty disposition are more dangerous than mountains or rivers; it takes a man of genius to penetrate such."So that we are left in some doubt as to his real opinion on the passage."]
16. They cannot be properly managed without benevolence and straightforwardness.
[Chang Yu says: "When you have attracted them by substantial offers, you must treat them with absolute sincerity;then they will work for you with all their might."]
17. Without subtle ingenuity of mind, one cannot make certain of the truth of their reports.
[Mei Yao-ch`en says: "Be on your guard against the possibility of spies going over to the service of the enemy."]
18. Be subtle! be subtle! and use your spies for every kind of business.
[Cf. VI. ss. 9.]
19. If a secret piece of news is divulged by a spy before the time is ripe, he must be put to death together with the man to whom the secret was told.
[Word for word, the translation here is: "If spy matters are heard before [our plans] are carried out," etc. Sun Tzu's main point in this passage is: Whereas you kill the spy himself "as a punishment for letting out the secret," the object of killing the other man is only, as Ch`en Hao puts it, "to stop his mouth" and prevent news leaking any further. If it had already been repeated to others, this object would not be gained. Either way, Sun Tzu lays himself open to the charge of inhumanity, though Tu Mu tries to defend him by saying that the man deserves to be put to death, for the spy would certainly not have told the secret unless the other had been at pains to worm it out of him."]
20. Whether the object be to crush an army, to storm a city, or to assassinate an individual, it is always necessary to begin by finding out the names of the attendants, the aides-de-camp,[Literally "visitors", is equivalent, as Tu Yu says, to "those whose duty it is to keep the general supplied with information," which naturally necessitates frequent interviews with him.]
and door-keepers and sentries of the general in command. Our spies must be commissioned to ascertain these.
[As the first step, no doubt towards finding out if any of these important functionaries can be won over by bribery.]
21. The enemy's spies who have come to spy on us must be sought out, tempted with bribes, led away and comfortably housed.
Thus they will become converted spies and available for our service.
