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[Tu Yu says: "through conversion of the enemy's spies we learn

the enemy's condition." And Chang Yu says: "We must tempt the

converted spy into our service, because it is he that knows which

of the local inhabitants are greedy of gain, and which of the

officials are open to corruption."]

23. It is owing to his information, again, that we can cause the

doomed spy to carry false tidings to the enemy.

[Chang Yu says, "because the converted spy knows how the enemy

can best be deceived."]

24. Lastly, it is by his information that the surviving spy can

be used on appointed occasions.

25. The end and aim of spying in all its five varieties is

knowledge of the enemy; and this knowledge can only be derived,

in the first instance, from the converted spy.

[As explained in §§ 22-24. He not only brings information

himself, but makes it possible to use the other kinds of spy to

advantage.]

Hence it is essential that the converted spy be treated with the

utmost liberality.