“Know your enemy, know his sword.”
“Combat doesn't have to be with swords... Emotions can be deadly weapons, and knowing your enemy's breaking point can be key to winning a battle.”
“Know your enemy — and learn about his favorite sport.”
“To know your Enemy, you must become your Enemy.”
“In order to know your enemy, you must become your enemy.”
“Know the enemy and know yourself; in a hundred battles you will never be in peril. When you are ignorant of the enemy, but know yourself, your chances of winning or losing are equal. If ignorant both of your enemy and yourself, you are certain in every battle to be in peril.”