Sun Tzu

On dispersive ground, therefore, fight not. On facile ground, halt not. On contentious ground, attack not.

you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.

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.

Hence the saying: One may know how to conquer without being able to do it.

Security against defeat implies defensive tactics; ability to defeat the enemy means taking the offensive.

Standing on the defensive indicates insufficient strength; attacking, a superabundance of strength.