Weakness in the opponent's position

Failing an opportunity for direct attack, one must attempt to increase whatever weakness there may be in the opponent's position; or, if there is none, one or more must be created. It is always an advantage to threaten something, but such threats must be carried into effect only if something is to be gained immediately. For, holding the threat in hand, forces the opponent to provide against its execution and to keep material in readiness to meet it. Thus he may more easily overlook, or be unable to parry, a thrust at another point. But once the threat is carried into effect, it exists no longer, and your opponent can devote his attention to his own schemes.