Art of War
"All warfare is based on deception. Hence, when we are able to attack, we must seem unable; when using our forces, we must appear inactive; when we are near, we must make the enemy believe we are far away..."--from Sun Tzu's Art of War. This is my take on this principle.
It's not what you know, it's how you show it. Show your enemy you are weak, even though you know you got a real badass weapon you can crush him with!