Those who are victorious plan effectively and change decisively. They are like a great river that maintains its course but adjusts its flow...they have form but are formless. They are skilled in both planning and adapting and need not fear the result of a thousand battles: for they win in advance, defeating those that have already lost.
When the common soldiers are too strong and their officers too weak, the result is insubordination. When the officers are too strong and the common soldiers too weak, the result is collapse.
We cannot enter into alliance with neighbouring princes until we are acquainted with their designs. We are not fit to lead an army on the march unless we are familiar with the face of the country - its mountains and forests, its pitfalls and precipices, its marshes and swamps. We shall be unable to turn natural advantages to account unless we make use of local guides.
The supreme excellence is not to win a hundred victories in a hundred battles. The supreme excellence is to subdue the armies of your enemies without having to fight them.
Confront them with annihilation, and they will then survive; plunge them into a deadly situation, and they will then live. When people fall into danger, they are then able to strive for victory.
So the principles of warfare are: Do not depend on the enemy not coming, but depend on our readiness against him. Do not depend on the enemy not attacking, but depend on our position that cannot be attacked.
The good fighters of old first put themselves beyond the possibility of defeat, and then waited for an opportunity of defeating the enemy. To secure ourselves against defeat lies in our own hands, but the opportunity of defeating the enemy is provided by the enemy himself. Thus the good fighter is able to secure himself against defeat, but cannot make certain of defeating the enemy.
Unless you know the mountains and the forests, the defiles and impasses, the lay of the marshes and swamps, you cannot maneuver with an armed force. Unless you use local guides, you cannot get the advantages of the land.