Sun Tzu distinguishes six kinds of terrain, and each one is a decision about who moves first. On accessible ground, which both sides can cross freely, be first onto the raised and sunny spots and guard the line of supplies. On entangling ground, which can be abandoned but is hard to re-occupy, sally out only if the enemy is unprepared. If he is ready and the attack fails, there is no return, and disaster follows. On temporising ground, where neither side gains by moving first, refuse the bait, retreat, and strike only when part of his army has been drawn out. A narrow pass is garrisoned strongly if you reach it first. If he is there already and the garrison is full, do not go after him. Go after him only if the pass is weakly held. Precipitous heights follow the same rule: take the sunny height and wait, or, if he has it, retreat and try to entice him down. At a great distance, with the two armies equal, it is not easy to provoke a battle, and fighting will be to your disadvantage. These six are the principles connected with Earth. The general in a responsible post has to study them.
The next six dangers are not in the ground. They are faults for which the general is responsible. Flight is what happens when one force is hurled against another ten times its size. Insubordination is what happens when the common soldiers are too strong and their officers too weak. Collapse is the reverse, officers strong and soldiers weak. Ruin is what happens when angry higher officers give battle on their own account, from resentment, before the commander-in-chief knows whether he is in a position to fight. Disorganisation is a weak general, unclear orders, no fixed duties, and ranks formed in a slovenly way. Rout is a general who cannot estimate the enemy's strength, sends an inferior force against a larger one, and neglects to place picked soldiers in the front rank.
The natural formation of the country is the soldier's best ally, but a power of estimating the adversary, of controlling the forces of victory, and of shrewdly calculating difficulties, dangers, and distances constitutes the test of a great general. He who knows these things and puts his knowledge into practice will win his battles. He who knows them not, nor practises them, will surely be defeated. If fighting is sure to result in victory, you must fight even though the ruler forbid it. If fighting will not result in victory, you must not fight even at the ruler's bidding. The general who advances without coveting fame and retreats without fearing disgrace, whose only thought is to protect his country and do good service for his sovereign, is the jewel of the kingdom. Regard your soldiers as your children, and they will follow you into the deepest valleys. Look upon them as your own beloved sons, and they will stand by you even unto death. If, however, you are indulgent but unable to make your authority felt, kind-hearted but unable to enforce your commands, and incapable of quelling disorder, then your soldiers are like spoilt children, useless for any practical purpose. Knowing that one's own men are in a condition to attack, but not that the enemy is not open to attack, is only halfway towards victory. Knowing that the enemy is open to attack, but not that one's own men are unfit to attack, is only halfway. Knowing both of those and not knowing that the ground makes fighting impracticable is still only halfway. The experienced soldier, once in motion, is never bewildered. Once he has broken camp, he is never at a loss. If you know the enemy and know yourself, your victory will not stand in doubt. If you know Heaven and know Earth, you may make your victory complete.
