6.9

"The ground where we join in battle must be unknowable [to the enemy]. If unknowable, then the places where the enemy must prepare will be many. If the places where the enemy must prepare is many, then the places where we join in battle will be few."
- Sun Tzu

This passage directly relates to the previous one. It is a fuller explanation of Sun Tzu's line where he says: "And if we, by means of our many, can strike his few, then the place by which we join in battle will be reduced."

For Sun Tzu, having a relative size advantage over the enemy is a matter of deception - blocking the enemy's knowledge of where and when to fight. This is why, for Sun Tzu, one must first occupy the ground of battle, and then do battle. One should never compete for already occupied ground.

If the place of battle is unknown to the enemy, then he will thin out his defenses preparing for an attack anywhere. Seeing this, a prepared general can select the few critical points at which he can send his soldiers to strike.

The point here works in your life as well: Your competitors should never know when or how you'll make a move. And where you should move should be where they are weakest or unprepared.