6. Weak Points and Strong
You can be sure of succeeding in your attacks if you only attack places which are undefended.
Wang Hsi explains "undefended places" as "weak points; that is to say, where the general is lacking in capacity, or the soldiers in spirit; where the walls are not strong enough, or the precautions not strict enough; where relief comes too late, or provisions are too scanty, or the defenders are variance amongst themselves."
I.e., where there are none of the weak points mentioned above. There is rather a nice point involved in the interpretation of this later clause. Tu Mu, Ch`en Hao, and Mei Yao-ch`en assume the meaning to be: "In order to make your defense quite safe, you must defend EVEN those places that are not likely to be attacked;" and Tu Mu adds: "How much more, then, those that will be attacked." Taken thus, however, the clause balances less well with the preceding—always a consideration in the highly antithetical style which is natural to the Chinese. Chang Yu, therefore, seems to come nearer the mark in saying: "He who is skilled in attack flashes forth from the topmost heights of heaven [see IV. ss. 7], making it impossible for the enemy to guard against him. This being so, the places that I shall attack are precisely those that the enemy cannot defend.... He who is skilled in defense hides in the most secret recesses of the earth, making it impossible for the enemy to estimate his whereabouts. This being so, the places that I shall hold are precisely those that the enemy cannot attack."