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.
Even the finest sword plunged into salt water will eventually rust.
If ignorant both of your enemy and yourself, you are certain to be in peril.
He who knows when he can fight and when he cannot, will be victorious.
There has never been a protracted war from which a country has benefited.
If you are far from the enemy, make him believe you are near.