In peace prepare for war, in war prepare for peace. The art of war is of vital importance to the state. It is matter of life and death, a road either to safety or to ruin. Hence under no circumstances can it be neglected.
If there is disturbance in the camp, the general's authority is weak. If the banners and flags are shifted about, sedition is afoot. If the officers are angry, it means that the men are weary.
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 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.
Do not engage an enemy more powerful than you. And if it is unavoidable and you do have to engage, then make sure you engage it on your terms, not on your enemy's terms.
These are the six ways of courting defeat - neglect to estimate the enemy's strength; want of authority; defective training; unjustifiable anger; nonobservance of discipline; failure to use picked men.
If we wish to fight, the enemy can be forced to an engagement even though he be sheltered behind a high rampart and a deep ditch. All we need do is attack some other place that he will be obliged to relieve.