The words of Sun Tzu Wu the Master:

1.  Calling 100,000 men to arms, and transporting them a hundred leagues, is such an undertaking that in one day 1,000 gold pieces of the citizens’ and nobles’ money are spent; commotions arise within and without the state; carriers fall down exhausted on the line of march of the army; and the occupations of 800,000 homes are upset.

2.  Again, for years the armies may face each other; yet the issue may depend on a single day’s victory.

3.  Wherefore, by grudging slight expense in titles and salaries to spies, to remain in ignorance of the enemy’s circumstances, is to be without humanity.  Such a person is no general; he is no assistance to his lord; he is no master of victory.

4.  The enlightened ruler and the wise general who act, win, and are distinguished beyond the common, are informed beforehand.

5.  This knowledge is not to be got by calling on gods and demons; nor does it come of past experience nor calculation. It is through men that knowledge of the enemy is gained.

6.  Now the five kinds of spies are these: village spies, inner spies, converted spies, death spies and living spies.

7.  If these five means be employed simultaneously, none can discover their working.  This is called the Mysterious Thread: it is the Prince’s Treasure.

8.  Village spies are such people of the country as give information.

9.  Inner spies are those of the enemy’s officials employed by us.

10.  Converted spies are those of the enemy’s spies in our pay.

11.  Death spies are sent to misinform the enemy, and to spread false reports through our spies already in the enemy’s lines.

12.  Living spies return to report.

13.  In connection with the armies, spies should be treated with the greatest kindness; and in dealing out reward, they should receive the most generous treatment.  All matters relating to spies are secret.

14.  Without infinite capacity in the general, the employment of spies is impossible.  Their treatment requires benevolence and uprightness.  Except they be observed with the closest attention, the truth will not be obtained from them.

15.  Wonderful indeed is the power of spies.

16.  There is no occasion when they cannot be used.

17.  If a secret matter be spoken of before the time is ripe, the spy who told the matter, and the man who repeated the same, should be put to death.

18.  If desirous of attacking an army; of besieging a fortress; or of killing a certain person; first of all, learn the names of the general in charge; of his right-hand men; of those who introduce visitors to the Presence; of the gate keeper and the sentries.  Then set the spies to watch them.

19.  Seek out the enemy’s spies who come to spy on us; give them money; cause them to be lodged and cared for; and convert them to the service.  Through them we are enabled to obtain spies among the enemy’s villagers and officials.

20.  By means of the converted spy, we can construct a false story for the death spy to carry to the enemy.

21.  It is through the converted spy that we are able to use the five varieties, to their utmost advantage; therefore he must be liberally treated.

22.  In ancient times the rise to power of the province of Yin was due to Ichih, who was sent to the country of Hsia.  Likewise during the foundation of the state of Chu, Luya lived among the people of Shang.

23.  Wherefore, intelligent rulers and wise generals use the cleverest men as spies, and invariably acquire great merit.  The spy is a necessity to the army.  Upon him the movement of the army depends.