If ignorant both of your enemy and yourself, you are certain to be in peril.
Birds rising in flight is a sign that the enemy is lying in ambush; when the wild animals are startled and flee he is trying to take you unaware.
The skillful leader subdues the enemy's troops without any fighting.
All war is based on deception.
The skilful employer of men will employ the wise man, the brave man, the covetous man, and the stupid man.
From a position of this sort, if the enemy is unprepared, you may sally forth and defeat him. But if the enemy is prepared for your coming, and you fail to defeat him, then, return being impossible, disaster will ensue.