the aggressor went on the attack, he had no more surprises in store—the defender could clearly see his strategy and take protective action. Second, if the defender could somehow turn back this initial attack, the aggressor would be left in a weak position; his army was disorganized and exhausted. (It requires more energy to take land than to hold it.) If the defenders could take advantage of this weakness to deliver a counterblow, they could often force the aggressor to retreat.
