The Nine Situations

The longest chapter of the book maps nine kinds of ground a campaign moves through and prescribes conduct for each. Dispersive ground is your own territory, where men think of home — do not fight there. Facile ground is shallow penetration into enemy land — do not halt. Contentious ground gives great advantage to whoever holds it — do not attack if the enemy holds it first. Open ground allows free movement — do not try to block the enemy's way. Ground of intersecting highways is the key terrain whose control commands alliances — join hands with your allies there. Serious ground is deep in hostile country with many fortified towns behind you — keep your army continuously supplied by foraging. Difficult ground — forests, marshes, broken country — keep marching through. On hemmed-in ground, where the way is narrow and retreat tortuous, resort to stratagem. On desperate ground, where you can only survive by fighting at once, you must fight.

The chapter's psychological core is the deliberate use of desperation. "Throw your soldiers into positions whence there is no escape, and they will prefer death to flight. If they will face death, there is nothing they may not achieve." Soldiers placed in deadly peril lose the sense of fear, stand firm with nowhere to run, fight hard because there is no alternative, and obey implicitly. "Place your army in deadly peril, and it will survive; plunge it into desperate straits, and it will come off in safety." The skilful general leads his men as though leading a single individual, by the hand, with no choice but to follow.

To make a host act as one body, Sun Tzu offers the image of the shuai-jan, the snake of Mt. Ch'ang: strike its head and the tail attacks; strike its tail and the head attacks; strike its middle and both head and tail attack together. A well-led army responds the same way — and men who would never cooperate willingly will help one another in extremity, "just as the left hand helps the right," when they are in the same boat caught in a storm.

The general's craft is secrecy and control. He keeps his own officers and men in ignorance of his deeper plans; he changes his arrangements and alters his routes so no one can read his purpose; "he burns his boats and breaks his cooking-pots" to signal there is no going back. He drives his men now this way, now that, like a shepherd driving a flock, and none knows the destination. Foreknowledge of the enemy's intent, gathered patiently, lets him then concentrate his whole force at the decisive point.

The closing counsel is for the moment of contact: be swift as a running hare once the door is open, take advantage of the enemy's unreadiness, travel by unexpected routes, and attack where he has taken no precautions. The enduring lesson is that commitment manufactures capability — remove the option of retreat, align everyone's survival with the same outcome, and an ordinary force will fight with the strength of one that has no other choice.