Military tactics are like unto water; for water in its natural course runs away from high places and hastens downwards... Water shapes its course according to the nature of the ground over which it flows; the soldier works out his victory in relation to the foe whom he is facing. Therefore, just as water retains no constant shape, so in warfare there are no constant conditions. He who can modify his tactics in relation to his opponent and thereby succeed in winning, may be called a heaven-born captain.

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

Maneuvering with an army is advantageous; with an undisciplined multitude, most dangerous.

Bring war material with you from home, but forage on the enemy... use the conquered foe to augment one's own strength.

He who is not sage and wise, humane and just, cannot use secret agent.s. And he who is not delicate and subtle cannot get the truth out of them.

Therefore, just as water retains no constant shape, so in warfare there are no constant conditions.

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