Sun Tzu emphasized the importance of using spies to seek the enemy situation in a special in this chapter. It is one of important of the military command. The army have to use military operations according to intelligence that spies are offer.
In the use of spies, Sun Tzu also proposed a five classes (1) Local spies; (2) inward spies; (3) converted spies; (4) doomed spies and (5) surviving spies. Emphasized the use of spies of all classes for open source of intelligence to extensive, make the enemy fall into confusion and does not know to cope. Meanwhile Sun Tzu was suggested that while used spies shall have the acumen. Courage and prudence. To prevent deceived from the enemy and use it as an advantage.