You can be sure of succeeding in your attacks if you only attack places which are undefended.You can ensure the safety of your defense if you only hold positions that cannot be attacked.
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.
He who is prudent and lies in wait for an enemy who is not, will be victorious.