Master Sun says the ruler gives orders to the general, who assembles the men and an army. Do not make camp on intractable terrain. Meet up with allies on crossroad terrain. Do not tarry on dire terrain. Use strategy on closed terrain. Engage in battle on death terrain.
Sun sets up the chapter with a brief summary of what has already been covered. Now, he has come to the matter of terrain. Sun offers specific advice on how to deal with each type of earthly barrier the general might face, in order to move through these places with the least effort and loss.
Some roads should be avoided, as should some enemies. Some towns should not be besieged, and some types of terrain should not be fought for. There are also orders from a ruler that one should not obey. The general that understands the nine changes knows war. Even if he knows the lay of the land, but is ignorant of the nine changes, he cannot put that knowledge to use. Even if he knows the five gains but not the nine changes, he cannot get the most from his men.
Some battles just aren’t worth fighting. Sometimes, the general will know better than his lord, and should act accordingly. But it is important that the general has truly deep perception and wisdom to apply the knowledge he has gained. Without such deeper insight, he cannot transform knowledge into success, and the men will not reach their potential.
When making decisions, the wise general considers both gain and harm. By not focusing on gain alone, he can be successful. By not focusing on harm, he can avoid disaster. He causes his enemy to surrender by harming him. The general keeps him busy to tire him. He distracts his enemy with thoughts of gain. The skillful general does not hope the enemy does not attack, but trusts his own preparations and defense.
The general must focus on all outcomes and eventualities, not blur his own perception with undue fear or arrogance. Instead, he distracts his enemy with such thoughts. The general does not hope the enemy will act in one way or another, as he keeps the enemy busy with his own devious schemes, and ensures his own invulnerability.
There are five ways a general can fail. Recklessness leads to annihilation. Cowardice leads to being caught. Anger leads to being easily baited. An overly sensitive sense of honor leads to embarrassment. Misplaced compassion for his men leads to trouble. These five excesses are not conducive to war. If an army is defeated and the general is killed, it is probably because of one of these pitfalls. Consider them above all.
The general’s own strength of mind and moral rectitude are hugely influential in war. His ability to lead rests on his own temperament as much as his military aptitude. It is not the men’s ability that determines victory, but the general’s presence of mind. In this case, it is key that a ruler picks a worthy general, and that the general keeps his own mind in mind.