If we know that our own men are in a condition to attack, but are unaware that the enemy is not open to attack, we have gone only halfway towards victory.

Invincibility lies in the defence; the possibility of victory in the attack.

Thus, what is of supreme importance in war is to attack the enemy's strategy.

Hence the saying: If you know the enemy and you know yourself, your victory will not stand in doubt; if you know Heaven and you know Earth, you may make your victory complete.

The opportunity to secure ourselves against defeat lies in our own hands, but the opportunity of defeating the enemy is provided by the enemy himself.

Know thy self, know thy enemy. A thousand battles, a thousand victories.