tting 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.
22. It is through the information brought by the converted
spy that we are able to acquire and employ local and inward
spies.

[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 ss. 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