Factors in the art of warfare are: First, calculations; second, quantities; third, logistics; fourth, the balance of power; and fifth, the possibility of victory is based on the balance of power.

No ruler should put troops into the field merely to gratify his own spleen; no general should fight a battle simply out of pique.

It is said that if you know your enemies and know yourself, you will not be imperiled in a hundred battles; if you do not know your enemies but do know yourself, you will win one and lose one; if you do not know your enemies nor yourself, you will be imperiled in every single battle.

Know thy self, know thy enemy.

The good fighter is able to secure himself against defeat, but cannot make certain of defeating the enemy.

So the important thing in a military operation is victory, not persistence.

If their forces are substantial, prepare for them; if their forces are strong, avoid them.