The Art of War is a Chinese military treatise that was written by Sun Tzu in the 6th century BC. It is said to be one of the definitive works on military strategies and tactics.
A few lines from the Art of War...
If you know your enemies and know yourself, you can win a hundred battles without a single loss. If you only know yourself, but not your opponent, you may win or may lose.
One hundred victories in one hundred battles is not the most skillful. Seizing the enemy without fighting is the most skillful.
All warfare is based on deception.
When able to attack, we must seem unable...hold out baits to entice the enemy. Feign disorder, and crush him.
If (your enemy) is in superior strength, evade him. If your opponent is temperamental, seek to irritate him. Pretend to be weak, that he may grow arrogant. If he is taking his ease, give him no rest. Attack him where he is unprepared, appear where you are not expected.
He who knows when he can fight and when he cannot will be victorious. He who is prudent and lies in wait for an enemy who is not, will be victorious.
Being unconquerable lies with yourself; being conquerable lies with your enemy.