9. Should the enemy forestall you in occupying a pass, do not go after him if the pass is fully garrisoned, but only if it is weakly garrisoned.

若敵先居之盈而勿從不盈而從之

Sun Tzu

Sun Tzu is talking about the strategic importance of avoiding conflicts when the enemy is in a strong position. In this case, the enemy has occupied a narrow pass before you and has fully garrisoned it, which means they have a strong defensive position. Sun Tzu is saying that in this situation, you should not try to attack the enemy directly. Instead, you should wait for an opportunity when the enemy’s garrison is weak and then attack. By avoiding a direct confrontation when the enemy is in a strong position, you can potentially save your own forces and gain an advantage.

If a competitor enters a narrow market before you, do not go after them if they have established a strong presence, but only if their position is weak.

If a competitor enters a narrow market before you and establishes a strong presence, it means that they have gained a foothold in the market and have a strategic advantage over you. In this situation, avoid going after the competitor directly, as this could potentially be costly and ineffective. Instead, you should wait for an opportunity when the competitor’s position is weak and then attack. By avoiding a direct confrontation when the competitor is in a strong position, you can potentially save your own resources and gain an advantage.