Knife, what is a knife? For those who wield the knife, they must remain calm in the face of danger, composed and unhurried, attacking when the enemy is unprepared, taking them by surprise. They remain unchanged when encountering an enemy, appear unfazed, have no sword in hand but harbor the sword in their heart. When the enemy moves, I stay still; when the enemy is still, I move; when the enemy chases, I run; when the enemy halts, I harass. Ię«their sharpness, disrupt their formations, force them to make mistakes, kill without leaving a trace, and harm from a thousand miles away...