Being unconquerable lies with yourself; being conquerable lies with your enemy.
Plan for what is difficult while it is easy, do what is great while it is small.
If you know yourself but not the enemy, for every victory gained you will also suffer a defeat.
Concentrate your energy and hoard your strength.
It is essential to seek out enemy agents who have come to conduct espionage against you and to bribe them to serve you. Give them instructions and care for them. Thus doubled agents are recruited and used.
The clever combatant looks to the effect of combined energy, and does not require too much from individuals. Hence his ability to pick out the right men and utilize combined energy