Chapter 9
Sun Tzu said: In leading troops and assessing enemy situations, one should pay attention to the following: When crossing mountains, advance near valleys and encamp on high, sunny ground. If the enemy occupies a height, do not attack uphill. These are the principles for deploying troops in mountainous terrain. When crossing rivers, encamp at a distance from the water. If the enemy crosses the river, do not engage them at the water's edge; wait until they are halfway across, then attack, for this is advantageous. When intending to engage the enemy, avoid facing them near water. When encamping along rivers, choose high, sunny ground and avoid facing the current. These are the principles for deploying troops in riverine areas. When crossing marshy salt flats, pass quickly and do not linger. If encountering the enemy in such terrain, rely on water and trees for protection. These are the principles for deploying troops in marshy areas. In open plains, encamp on flat ground with high ground to the right and a slope descending to the front and rising to the rear. These are the principles for deploying troops in plains. The benefits of these four types of deployments were the reasons why the Yellow Emperor defeated the Four Emperors.
Generally, troops prefer to encamp on dry, high ground and avoid wet, low-lying areas; they favor sunny spots and avoid shady places; and they seek out grassy areas near water to avoid diseases, ensuring victory. On hills and embankments, encamp on the sunny side with the right side relying on them. These are the advantageous conditions for warfare, aided by the terrain. When it rains upstream, foam will drift downstream. If crossing a river, wait until the foam settles. In terrain with features like deep ravines, natural pits, enclosed spaces, entangling networks, traps, and gaps, one must leave swiftly and avoid approaching them. Keep your distance from them while forcing the enemy to approach; face them while having the enemy's back to them. When advancing through difficult and dangerous terrain, such as reeds-covered lowlands and dense forests, search cautiously, as these are places where enemy spies and ambush forces may hide.
If the enemy approaches quietly, they rely on occupying advantageous terrain. If the enemy comes from afar to challenge, they intend to lure us forward. If the enemy abandons advantageous positions and occupies flat ground, they must have some benefit or intention. If many trees sway ahead, it indicates the enemy is approaching under cover. If there are many obstacles in the grass, it is a decoy set by the enemy. If birds fly up in alarm, there are ambush forces below. If wild animals are frightened, it indicates a surprise attack by a large force. If dust rises high into the sky, it signifies the approach of chariots. If dust rises low and spreads widely, it signifies the arrival of infantry. If dust is scattered, it means the enemy is dragging logs. If dust is sparse and rises intermittently, it means the enemy is encamping. If the enemy's messengers are humble but preparations for war are intensified, they intend to attack. If the enemy's messengers are harsh and the advance guard pushes forward, they are preparing to retreat. If light chariots move out first and are deployed on both wings, they are arranging their formation. If the enemy seeks peace without being defeated, they have another scheme. If the enemy runs swiftly and arranges their troops in formation, they intend to engage in decisive battle. If the enemy advances and retreats alternately, they are trying to lure us forward. If the enemy leans on their weapons while standing, it indicates hunger. If soldiers are sent to fetch water and drink first, it indicates thirst. If the enemy sees an advantage but does not advance to seize it, it indicates fatigue. If birds gather over the enemy's camp, the camp must be empty. If there are cries at night in the enemy's camp, it indicates fear among the troops. If the enemy is in disorder, it indicates the commander lacks authority. If the enemy's flags are in disarray, it indicates the camp is in chaos. If the enemy's officers are angry, it is a sign of extreme fatigue. If grain is fed to horses and livestock is killed for food, and there are no water buckets hanging in the camp, indicating a determination not to return, the enemy is preparing to break out. If the commander speaks humbly to his subordinates, it indicates he has lost their support. If soldiers are constantly rewarded, it indicates the enemy is desperate. If subordinates are constantly punished, it indicates the enemy is in a difficult situation. If the commander is first cruel to his soldiers and then fears their rebellion, he is an extremely foolish leader. If gifts are brought for negotiations, it indicates a desire for peace. If the enemy comes in anger but does not engage in battle for a long time nor withdraws, one must carefully examine their intentions.
War is not about having a large number of troops; rather, it is about not relying on bravery and rushing into battle. It is about being united, accurately assessing the enemy, and defeating them. Those who lack foresight and underestimate the enemy will surely be captured.
If soldiers are punished before they become attached, they will flee and be difficult to use; if soldiers are attached but discipline is not enforced, they will be unusable. Therefore, educate soldiers through politics and regulations, and unify their actions through military discipline and laws. Only then will they be an unbeatable force. If commands are strictly enforced and soldiers are disciplined in peacetime, they will obey. If commands are not strictly enforced, discipline is not upheld, and trust is not established with soldiers, they will not obey. If commands are reliable and verified in peacetime, and soldiers are in harmony, they can share life and death together.
