Those who do not know the plans of competitors cannot prepare alliances. Those who do not know the lay of the land cannot maneuver their forces. Those who do not use local guides cannot take advantage of the ground.
By altering his arrangements and changing his plans, the skillful general keeps the enemy without definite knowledge. By shifting his camp and taking circuitous routes, he prevents the enemy from anticipating his purpose. At the critical moment, the leader of an army acts like one who has climbed up a height and then kicks away the ladder behind him.
Thus the highest form of generalship is to balk the enemy's plans, the next best is to prevent the junction of the enemy's forces, the next in order is to attack the enemy's army in the field, and the worst policy of all is to besiege walled cities.
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.
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.
Hostile armies may face each other for years, striving for the victory which is decided in a single day. This being so, to remain in ignorance of the enemy's condition simply because one grudges the outlay of a hundred ounces of silver in honors and emoluments, is the height of inhumanity.
You cannot know if you will be successful or not. You can only prepare for battle and it must be done with all of your heart and with all of your consciousness. In that manner, you will have an edge.